Determining multipath in a positioning system

ABSTRACT

Methods, systems, computer-readable media, and apparatuses for determination of multipath for determining a location of user equipment (UE) are presented. In some embodiments, the UE may, based on a first indication of signal strength associated with a first polarization type, and a second indication of signal strength associated with a second polarization type, determine an indication of multipath reflection along a path of signal propagation between a space vehicle (e.g., GNSS satellite) and the UE. Circularly polarized positioning signals may be received by the UE via natively present linearly polarized antennas and converted into circularly polarized signals. Converted circularly polarized signals may include right-handed and left-handed components, and signal strengths for each component may be compared to determine the presence of multipath. Positioning signals may be given a weight or disregarded based on the multipath determination when determining the position of the UE.

BACKGROUND 1. Field of Disclosure

Aspects of the present disclosure generally relate to the field ofwireless communications, particularly satellite communications, anddetermination of one or more properties of a User Equipment (UE) usingradio frequency (RF) signals.

2. Description of Related Technology

The determination of a position of a mobile UE in a wirelesscommunication network, often referred to as “positioning” of the UE, maybe performed using any of a variety of position-determining techniques.

One example of such techniques includes transmission of referencesignals by one or more Transmission Reception Points (TRPs) of thewireless communication network, and the measurement of these referencesignals by the UE. These measurements can be indicative of distancesand/or angles between the UE and one or more TRPs, enabling the positionof the UE to be determined using multiangulation, multilateration (e.g.,trilateration), and/or other geospatial or geometric (e.g., geodetic orgeocentric) techniques.

The position determination of a UE often uses multiple measurementsinvolving multiple reference signals. And each reference signal may beidentified uniquely by both the network and UE. Reference signals aretypically part of a large hierarchical structure and may require a largeamount of signaling overhead to uniquely identify.

Other positioning techniques involving signal strength and/or othernetwork parameters (as discussed elsewhere herein) may also be usedalone or in conjunction with the foregoing techniques.

However, none of these techniques can fully and reliably eliminatepositioning problems, in particular those caused by multipathpropagation of radio signals. In radio communication, so-calledmultipath may refer to radio signals reaching a receiver (e.g., areceiving antenna located in a UE) by two or more paths. For example, asignal emitted from a space vehicle (SV), such as a satellite used insatellite navigation systems (e.g., a Global Navigation Satellite System(GNSS) such as the Global Positioning System (GPS), Galileo, etc.), mayreflect off various surfaces near the globe's surface (e.g., naturalenvironmental obstacles, walls of structures, doors, tunnels, roads)before reaching a UE. This propagation of the signal along two or morepaths causes degradation of the signal from the SV, which may causeerrors or delays in determining the location of a UE (or otherreceiver-equipped device) via one or more of the techniques describedabove.

In fact, multipath continues to remain a dominant source of errors inpositioning. While multipath cannot be completely eliminated, given thatthere always exist locations without a direct line of sight from an SV,what is needed is a reliable way to indicate that a received positioningsignal does or does not have multipath on it, and to what extent.

To these ends, solutions are described herein to, among other things,provide UEs an additional set of techniques to increase thedetectability of multipath and thereby further optimize the reliabilityof positioning.

BRIEF SUMMARY

In one aspect of the present disclosure, a method for multipathestimation at a mobile device is disclosed. In some embodiments, themethod includes: determining a first indication of signal strengthassociated with a first polarization type and derived from one or moresignals received from a GNSS satellite using one or more antennas at themobile device; determining a second indication of signal strengthassociated with a second polarization type and derived from the one ormore signals received from the GNSS satellite using the one or moreantennas at the mobile device; and based on the first indication ofsignal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determining an indication of multipath reflectionalong a path of signal propagation between the GNSS satellite and themobile device.

In another aspect of the present disclosure, a user equipment isdisclosed. In some embodiments, the user equipment includes a basebandsubsystem; an antenna subsystem configured for signal communication withthe baseband subsystem, the antenna subsystem comprising a firstantenna, a second antenna, and a radio frequency (RF) coupler configuredto receive signal inputs from the first antenna and the second antennato output a signal having a first polarization type and a signal havinga second polarization type; and a processor, communicatively connectedto the baseband subsystem, the processor configured to: determine afirst indication of signal strength associated with the firstpolarization type and derived from one or more signals received from aGNSS satellite using the antenna subsystem; determine a secondindication of signal strength associated with the second polarizationtype and derived from the one or more signals received from the GNSSsatellite using the antenna subsystem; and based on the first indicationof signal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determine an indication of multipath reflection alonga path of signal propagation between the GNSS satellite and the userequipment.

In another aspect of the present disclosure, a non-transitorycomputer-readable apparatus is disclosed. In some embodiments, thenon-transitory computer-readable apparatus includes a storage medium,the storage medium including a plurality of instructions to, whenexecuted by a processor, cause a mobile device to: determine a firstindication of signal strength associated with a first polarization typeand derived from one or more signals received from a GNSS satelliteusing one or more antennas at the mobile device; determine a secondindication of signal strength associated with a second polarization typeand derived from the one or more signals received from the GNSSsatellite using the one or more antennas at the mobile device; and basedon the first indication of signal strength associated with the firstpolarization type and the second indication of signal strengthassociated with the second polarization type, determine an indication ofmultipath reflection along a path of signal propagation between the GNSSsatellite and the mobile device.

In another aspect of the present disclosure, a computerized apparatus isdisclosed. In some embodiments, the computerized apparatus includes:means for determining a first indication of signal strength associatedwith a first polarization type and derived from one or more signalsreceived from a GNSS satellite using one or more antennas; means fordetermining a second indication of signal strength associated with asecond polarization type and derived from the one or more signalsreceived from the GNSS satellite using the one or more antennas; andmeans for, based on the first indication of signal strength associatedwith the first polarization type and the second indication of signalstrength associated with the second polarization type, determining anindication of multipath reflection along a path of signal propagationfrom the GNSS satellite.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are illustrated by way of example inthe accompanying figures:

FIG. 1 illustrates a diagram of an embodiment of a positioning systemthat may be useful with one or more embodiments of the presentdisclosure.

FIG. 2 illustrates a diagram of an embodiment of a positioning system(e.g., the positioning system of FIG. 1 ) implemented within a 5thGeneration New Radio (5G NR) communication system.

FIG. 3 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using an RFcoupler and a single signal path to transmit time-multiplexed,circularly polarized signals from the antenna subsystem to the basebandsubsystem, according to one embodiment.

FIG. 4 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using twosignal paths configured to transmit circularly polarized signals fromthe antenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 5 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using a singlesignal path to transmit frequency-multiplexed, circularly polarizedsignals from the antenna subsystem to the baseband subsystem, accordingto one embodiment.

FIG. 6 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using twosignal paths to transmit digitized, circularly polarized signals fromthe antenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 7 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using onesignal path to transmit digitized, circularly polarized signals from theantenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 8 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using twosignal paths configured to transmit linearly polarized signals from theantenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 9 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using a singlesignal path to transmit frequency-multiplexed, linearly polarizedsignals from the antenna subsystem to the baseband subsystem, accordingto one embodiment.

FIG. 10 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using twosignal paths to transmit digitized, linearly polarized signals from theantenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 11 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using onesignal path to transmit digitized, linearly polarized signals from theantenna subsystem to the baseband subsystem, according to oneembodiment.

FIG. 12 illustrates a block diagram of a configuration of an antennasubsystem and a baseband subsystem of a wireless device, using anextractor, a diplexer, and/or a 90-degree hybrid coupler, according toone embodiment.

FIG. 13 is a table showing illustrative examples of determinations thatmay be made regarding multipath and classifications of environmentalcontexts based on right-handed and left-handed components of positioningsignals.

FIG. 14 illustrates a flow diagram of a method of determining thepresence of multipath during positioning of a mobile device, accordingto one embodiment.

FIG. 15 illustrates a flow diagram of a method of determining thepresence of multipath during positioning of a mobile device, accordingto another embodiment.

FIG. 16 is a block diagram of an embodiment of a UE, which can beutilized in embodiments as described herein.

FIG. 17 is a block diagram of an embodiment of an enhanced repeaterapparatus, which can be utilized in embodiments as described herein.

DETAILED DESCRIPTION

Several illustrative embodiments will now be described with respect tothe accompanying drawings, which form a part hereof. While particularembodiments, in which one or more aspects of the disclosure may beimplemented, are described below, other embodiments may be used andvarious modifications may be made without departing from the scope ofthe disclosure or the spirit of the appended claims.

The following description is directed to certain implementations for thepurposes of describing innovative aspects of various embodiments.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, system, or network that is capable of transmitting and receivingradio frequency (RF) signals according to any communication standard,such as any of the Institute of Electrical and Electronics Engineers(IEEE) IEEE 802.11 standards (including those identified as Wi-Fi®technologies), the Bluetooth® standard, code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), Global System for Mobile communications (GSM),GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment(EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA),Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B,High Rate Packet Data (HRPD), High Speed Packet Access (HSPA), HighSpeed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access(HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution(LTE), Advanced Mobile Phone System (AMPS), or other known signals thatare used to communicate within a wireless, cellular or internet ofthings (IoT) network, such as a system utilizing 3G, 4G, 5G, 6G, orfurther implementations thereof, technology.

As used herein, an “RF signal” comprises an electromagnetic wave thattransports information through the space between a transmitter (ortransmitting device) and a receiver (or receiving device). As usedherein, a transmitter may transmit a single “RF signal” or multiple “RFsignals” to a receiver. However, the receiver may receive multiple “RFsignals” corresponding to each transmitted RF signal due to thepropagation characteristics of RF signals through multipath channels.The same transmitted RF signal on different paths between thetransmitter and receiver may be referred to as a “multipath” RF signal.

Additionally, references to “reference signals,” “positioning referencesignals,” “reference signals for positioning,” and the like may be usedto refer to signals used for positioning of a user equipment (UE). Asdescribed in more detail herein, such signals may comprise any of avariety of signal types but may not necessarily be limited to aPositioning Reference Signal (PRS) as defined in relevant wirelessstandards.

As discussed above, multipath propagation poses an issue for receivingpositioning signals and determining a location of a UE. Additionaldetails addressing multipath will follow an initial description ofrelevant systems and technologies.

FIG. 1 is a simplified illustration of a positioning system 100 in whicha UE 105, location server 160, and/or other components of thepositioning system 100 can use the techniques provided herein fordetermination and assessment of multipath for determining a location ofthe UE, according to an embodiment. The techniques described herein maybe implemented by one or more components of the positioning system 100.The positioning system 100 can include: a UE 105; one or more satellites110 (also referred to as space vehicles (SVs)) for a Global NavigationSatellite System (GNSS) such as the Global Positioning System (GPS),GLONASS, Galileo or Beidou; base stations 120; access points (APs) 130;location server 160; network 170; and external client 180. Generallyput, the positioning system 100 can estimate a location of the UE 105based on RF signals received by and/or sent from the UE 105 and knownlocations of other components (e.g., GNSS satellites 110, base stations120, APs 130) transmitting and/or receiving the RF signals. Additionaldetails regarding particular location estimation techniques arediscussed in more detail with regard to FIG. 2 .

It should be noted that FIG. 1 provides only a generalized illustrationof various components, any or all of which may be utilized asappropriate, and each of which may be duplicated as necessary.Specifically, although only one UE 105 is illustrated, it will beunderstood that many UEs (e.g., hundreds, thousands, millions, etc.) mayutilize the positioning system 100. Similarly, the positioning system100 may include a larger or smaller number of base stations 120 and/orAPs 130 than illustrated in FIG. 1 . The illustrated connections thatconnect the various components in the positioning system 100 comprisedata and signaling connections which may include additional(intermediary) components, direct or indirect physical and/or wirelessconnections, and/or additional networks. Furthermore, components may berearranged, combined, separated, substituted, and/or omitted, dependingon desired functionality. In some embodiments, for example, the externalclient 180 may be directly connected to location server 160. A person ofordinary skill in the art will recognize many modifications to thecomponents illustrated.

Depending on desired functionality, the network 170 may comprise any ofa variety of wireless and/or wireline networks. The network 170 can, forexample, comprise any combination of public and/or private networks,local and/or wide-area networks, and the like. Furthermore, the network170 may utilize one or more wired and/or wireless communicationtechnologies. In some embodiments, the network 170 may comprise acellular or other mobile network, a wireless local area network (WLAN),a wireless wide-area network (WWAN), and/or the Internet, for example.Examples of network 170 include a Long-Term Evolution (LTE) wirelessnetwork, a Fifth Generation (5G) wireless network (also referred to asNew Radio (NR) wireless network or 5G NR wireless network), a Wi-FiWLAN, and the Internet. LTE, 5G and NR are wireless technologiesdefined, or being defined, by the 3rd Generation Partnership Project(3GPP). Network 170 may also include more than one network and/or morethan one type of network.

The base stations (BS) 120 and access points (APs) 130 may be configuredto be communicatively coupled to the network 170. In some embodiments,the base stations 120 may be owned, maintained, and/or operated by acellular network provider, and may employ any of a variety of wirelesstechnologies, as described herein below. Depending on the technology ofthe network 170, a base station 120 may comprise a node B, an EvolvedNode B (eNodeB or eNB), a base transceiver station (BTS), a radio basestation (RBS), an NR NodeB (gNB), a Next Generation eNB (ng-eNB), or thelike. A base station 120 that is a gNB or ng-eNB may be part of a NextGeneration Radio Access Network (NG-RAN) which may connect to a 5G CoreNetwork (5GC) in the case that Network 170 is a 5G network. An AP 130may comprise a Wi-Fi AP or a Bluetooth® AP or an AP having cellularcapabilities (e.g., 4G LTE and/or 5G NR), for example. Thus, UE 105 cansend and receive information with network-connected devices, such aslocation server 160, by accessing the network 170 via a base station 120using a first communication link 133. Additionally or alternatively,because APs 130 also may be communicatively coupled with the network170, UE 105 may communicate with network-connected andInternet-connected devices, including location server 160, using asecond communication link 135, or via one or more other UEs 145.

As used herein, the term “base station” may generically refer to asingle physical transmission point, or multiple co-located physicaltransmission points, which may be located at a base station 120. ATransmission Reception Point (TRP) (also known as transmit/receivepoint) corresponds to this type of transmission point, and the term“TRP” may be used interchangeably herein with the terms “gNB,” “ng-eNB,”and “base station.” In some cases, a base station 120 may comprisemultiple TRPs—e.g. with each TRP associated with a different antenna ora different antenna array for the base station 120. Physicaltransmission points may comprise an array of antennas of a base station120 (e.g., as in a Multiple Input-Multiple Output (MIMO) system and/orwhere the base station employs beamforming). The term “base station” mayadditionally refer to multiple non-co-located physical transmissionpoints, the physical transmission points may be a Distributed AntennaSystem (DAS) (a network of spatially separated antennas connected to acommon source via a transport medium) or a Remote Radio Head (RRH) (aremote base station connected to a serving base station).

As used herein, the term “cell” may generically refer to a logicalcommunication entity used for communication with a base station 120, andmay be associated with an identifier for distinguishing neighboringcells (e.g., a Physical Cell Identifier (PCID), a Virtual CellIdentifier (VCID)) operating via the same or a different carrier. Insome examples, a carrier may support multiple cells, and different cellsmay be configured according to different protocol types (e.g.,Machine-Type Communication (MTC), Narrowband Internet-of-Things(NB-IoT), Enhanced Mobile Broadband (eMBB), or others) that may provideaccess for different types of devices. In some cases, the term “cell”may refer to a portion of a geographic coverage area (e.g., a sector)over which the logical entity operates.

The location server 160 may comprise a server and/or other computingdevice configured to determine an estimated location of UE 105 and/orprovide data (e.g., “assistance data”) to UE 105 to facilitate locationmeasurement and/or location determination by UE 105. According to someembodiments, location server 160 may comprise a Home Secure User PlaneLocation (SUPL) Location Platform (H-SLP), which may support the SUPLuser plane (UP) location solution defined by the Open Mobile Alliance(OMA) and may support location services for UE 105 based on subscriptioninformation for UE 105 stored in location server 160. In someembodiments, the location server 160 may comprise, a Discovered SLP(D-SLP) or an Emergency SLP (E-SLP). The location server 160 may alsocomprise an Enhanced Serving Mobile Location Center (E-SMLC) thatsupports location of UE 105 using a control plane (CP) location solutionfor LTE radio access by UE 105. The location server 160 may furthercomprise a Location Management Function (LMF) that supports location ofUE 105 using a control plane (CP) location solution for NR or LTE radioaccess by UE 105.

In a CP location solution, signaling to control and manage the locationof UE 105 may be exchanged between elements of network 170 and with UE105 using existing network interfaces and protocols and as signalingfrom the perspective of network 170. In a UP location solution,signaling to control and manage the location of UE 105 may be exchangedbetween location server 160 and UE 105 as data (e.g. data transportedusing the Internet Protocol (IP) and/or Transmission Control Protocol(TCP)) from the perspective of network 170.

As previously noted (and discussed in more detail below), the estimatedlocation of UE 105 may be based on measurements of RF signals sent fromand/or received by the UE 105. In particular, these measurements canprovide information regarding the relative distance and/or angle of theUE 105 from one or more components in the positioning system 100 (e.g.,GNSS satellites 110, APs 130, base stations 120). The estimated locationof the UE 105 can be estimated geometrically (e.g., usingmultiangulation and/or multilateration), based on the distance and/orangle measurements, along with known position of the one or morecomponents.

Although terrestrial components such as APs 130 and base stations 120may be fixed, embodiments are not so limited. Mobile components may beused. For example, in some embodiments, a location of the UE 105 may beestimated at least in part based on measurements of RF signals 140communicated between the UE 105 and one or more other UEs 145, which maybe mobile or fixed. When or more other UEs 145 are used in the positiondetermination of a particular UE 105, the UE 105 for which the positionis to be determined may be referred to as the “target UE,” and each ofthe one or more other UEs 145 used may be referred to as an “anchor UE.”For position determination of a target UE, the respective positions ofthe one or more anchor UEs may be known and/or jointly determined withthe target UE. Direct communication between the one or more other UEs145 and UE 105 may comprise sidelink and/or similar Device-to-Device(D2D) communication technologies. Sidelink, which is defined by 3GPP, isa form of D2D communication under the cellular-based LTE and NRstandards.

An estimated location of UE 105 can be used in a variety of applications— e.g. to assist direction finding or navigation for a user of UE 105 orto assist another user (e.g. associated with external client 180) tolocate UE 105. A “location” is also referred to herein as a “locationestimate”, “estimated location”, “location”, “position”, “positionestimate”, “position fix”, “estimated position”, “location fix” or“fix”. The process of determining a location may be referred to as“positioning,” “position determination,” “location determination,” orthe like. A location of UE 105 may comprise an absolute location of UE105 (e.g. a latitude and longitude and possibly altitude) or a relativelocation of UE 105 (e.g. a location expressed as distances north orsouth, east or west and possibly above or below some other known fixedlocation (including, e.g., BS 120 or AP 130) or some other location suchas a location for UE 105 at some known previous time, or a location ofanother UE 145). A location may be specified as a geodetic locationcomprising coordinates which may be absolute (e.g. latitude, longitudeand optionally altitude), relative (e.g. relative to some known absolutelocation) or local (e.g. X, Y and optionally Z coordinates according toa coordinate system defined relative to a local area such a factory,warehouse, college campus, shopping mall, sports stadium or conventioncenter). A location may instead be a civic location and may thencomprise one or more of a street address (e.g. including names or labelsfor a country, state, county, city, road and/or street, and/or a road orstreet number), and/or a label or name for a place, building, portion ofa building, floor of a building, and/or room inside a building etc. Alocation may further include an uncertainty or error indication, such asa horizontal and possibly vertical distance by which the location isexpected to be in error or an indication of an area or volume (e.g. acircle or ellipse) within which UE 105 is expected to be located withsome level of confidence (e.g. 95% confidence).

The external client 180 may be a web server or remote application thatmay have some association with UE 105 (e.g. may be accessed by a user ofUE 105) or may be a server, application, or computer system providing alocation service to some other user or users which may include obtainingand providing the location of UE 105 (e.g. to enable a service such asfriend or relative finder, or child or pet location). Additionally oralternatively, the external client 180 may obtain and provide thelocation of UE 105 to an emergency services provider, government agency,etc.

As previously noted, the example positioning system 100 can beimplemented using a wireless communication network, such as an LTE-basedor 5G NR-based network. FIG. 2 shows a diagram of a 5G NR positioningsystem 200, illustrating an embodiment of a positioning system (e.g.,positioning system 100) implementing 5G NR. The 5G NR positioning system200 may be configured to determine the location of a UE 105 by usingaccess nodes (which may correspond with base stations 120 and accesspoints 130 of FIG. 1 ) and (optionally) an LMF 220 (which may correspondwith location server 160) to implement one or more positioning methods.Here, the 5G NR positioning system 200 comprises a UE 105, andcomponents of a 5G NR network comprising a Next Generation (NG) RadioAccess Network (RAN) (NG-RAN) 235 and a 5G Core Network (5G CN) 240. A5G network may also be referred to as an NR network; NG-RAN 235 may bereferred to as a 5G RAN or as an NR RAN; and 5G CN 240 may be referredto as an NG Core network. The 5G NR positioning system 200 may furtherutilize information from GNSS satellites 110 from a GNSS system likeGlobal Positioning System (GPS) or similar system (e.g. GLONASS,Galileo, Beidou, Indian Regional Navigational Satellite System (IRNSS)).Additional components of the 5G NR positioning system 200 are describedbelow. The 5G NR positioning system 200 may include additional oralternative components.

It should be noted that FIG. 2 provides only a generalized illustrationof various components, any or all of which may be utilized asappropriate, and each of which may be duplicated or omitted asnecessary. Specifically, although only one UE 105 is illustrated, itwill be understood that many UEs (e.g., hundreds, thousands, millions,etc.) may utilize the 5G NR positioning system 200. Similarly, the 5G NRpositioning system 200 may include a larger (or smaller) number of GNSSsatellites 110, gNBs 210 (which may be examples of base stations),ng-eNBs 214, Wireless Local Area Networks (WLANs) 216, Access andmobility Management Functions (AMFs) 215, external clients 230, and/orother components. The illustrated connections that connect the variouscomponents in the 5G NR positioning system 200 include data andsignaling connections which may include additional (intermediary)components, direct or indirect physical and/or wireless connections,and/or additional networks. Furthermore, components may be rearranged,combined, separated, substituted, and/or omitted, depending on desiredfunctionality.

The UE 105 may comprise and/or be referred to as a device, a mobiledevice, a wireless device, a mobile terminal, a terminal, a mobilestation (MS), a Secure User Plane Location (SUPL)-Enabled Terminal(SET), or by some other name. Moreover, UE 105 may correspond to acellphone, smartphone, laptop, tablet, personal data assistant (PDA),navigation device, Internet of Things (IoT) device, or some otherportable or moveable device. Typically, though not necessarily, the UE105 may support wireless communication using one or more Radio AccessTechnologies (RATs) such as using GSM, CDMA, W-CDMA, LTE, High RatePacket Data (HRPD), IEEE 802.11 Wi-Fi®, Bluetooth, WorldwideInteroperability for Microwave Access (WiMAXTM), 5G NR (e.g., using theNG-RAN 235 and 5G CN 240), etc. The UE 105 may also support wirelesscommunication using a WLAN 216 which (like the one or more RATs, and aspreviously noted with respect to FIG. 1 ) may connect to other networks,such as the Internet. The use of one or more of these RATs may allow theUE 105 to communicate with an external client 230 (e.g., via elements of5G CN 240 not shown in FIG. 2 , or possibly via a Gateway MobileLocation Center (GMLC) 225) and/or allow the external client 230 toreceive location information regarding the UE 105 (e.g., via the GMLC225). The external client 230 of FIG. 2 may correspond to externalclient 180 of FIG. 1 , as implemented in or communicatively coupled witha 5G NR network.

The UE 105 may include a single entity or may include multiple entities,such as in a personal area network where a user may employ audio, videoand/or data I/O devices, and/or body sensors and a separate wireline orwireless modem. An estimate of a location of the UE 105 may be referredto as a location, location estimate, location fix, fix, position,position estimate, or position fix, and may be geodetic, thus providinglocation coordinates for the UE 105 (e.g., latitude and longitude),which may or may not include an altitude component (e.g., height abovesea level, height above or depth below ground level, floor level orbasement level). Alternatively, a location of the UE 105 may beexpressed as a civic location (e.g., as a postal address or thedesignation of some point or small area in a building such as aparticular room or floor). A location of the UE 105 may also beexpressed as an area or volume (defined either geodetically or in civicform) within which the UE 105 is expected to be located with someprobability or confidence level (e.g., 67%, 95%, etc.). A location ofthe UE 105 may further be a relative location comprising, for example, adistance and direction or relative X, Y (and Z) coordinates definedrelative to some origin at a known location which may be definedgeodetically, in civic terms, or by reference to a point, area, orvolume indicated on a map, floor plan or building plan. In thedescription contained herein, the use of the term location may compriseany of these variants unless indicated otherwise. When computing thelocation of a UE, it is common to solve for local X, Y, and possibly Zcoordinates and then, if needed, convert the local coordinates intoabsolute ones (e.g. for latitude, longitude and altitude above or belowmean sea level).

Base stations in the NG-RAN 235 shown in FIG. 2 may correspond to basestations 120 in FIG. 1 and may include NR NodeB (gNB) 210-1 and 210-2(collectively and generically referred to herein as gNBs 210). Pairs ofgNBs 210 in NG-RAN 235 may be connected to one another (e.g., directlyas shown in FIG. 2 or indirectly via other gNBs 210). The communicationinterface between base stations (e.g., gNBs 210 and/or ng-eNB 214) maybe referred to as an Xn interface 237. Access to the 5G network isprovided to UE 105 via wireless communication between the UE 105 and oneor more of the gNBs 210, which may provide wireless communicationsaccess to the 5G CN 240 on behalf of the UE 105 using 5G NR. Thewireless interface between base stations (e.g., gNBs 210 and/or ng-eNB214) and the UE 105 may be referred to as a Uu interface 239. 5G NRradio access may also be referred to as NR radio access or as 5G radioaccess. In FIG. 2 , the serving gNB for UE 105 is assumed to be gNB210-1, although other gNBs (e.g. gNB 210-2) may act as a serving gNB ifUE 105 moves to another location or may act as a secondary gNB toprovide additional throughput and bandwidth to UE 105.

Base stations in the NG-RAN 235 shown in FIG. 2 may also or insteadinclude a next generation evolved Node B, also referred to as an ng-eNB,214. Ng-eNB 214 may be connected to one or more gNBs 210 in NG-RAN 235,e.g., directly or indirectly via other gNBs 210 and/or other ng-eNBs. Anng-eNB 214 may provide LTE wireless access and/or evolved LTE (eLTE)wireless access to UE 105. Some gNBs 210 (e.g. gNB 210-2 and/or anothergNB not shown) and/or ng-eNB 214 in FIG. 2 may be configured to functionas positioning-only beacons which may transmit signals (e.g.,Positioning Reference Signal (PRS)) and/or may broadcast assistance datato assist positioning of UE 105 but may not receive signals from UE 105or from other UEs. It is noted that while only one ng-eNB 214 is shownin FIG. 2 , some embodiments may include multiple ng-eNBs 214. Basestations may communicate directly with one another via an Xncommunication interface. Additionally or alternatively, base stationsmay communicate directly or indirectly with other components of the 5GNR positioning system 200, such as the LMF 220 and AMF 215.

5G NR positioning system 200 may also include one or more WLANs 216which may connect to a Non-3GPP InterWorking Function (N3IWF) 250 in the5G CN 240 (e.g., in the case of an untrusted WLAN 216). For example, theWLAN 216 may support IEEE 802.11 Wi-Fi access for UE 105 and maycomprise one or more Wi-Fi APs (e.g., APs 130 of FIG. 1 ). Here, theN3IWF 250 may connect to other elements in the 5G CN 240 such as AMF215. In some embodiments, WLAN 216 may support another RAT such asBluetooth. The N3IWF 250 may provide support for secure access by UE 105to other elements in 5G CN 240 and/or may support interworking of one ormore protocols used by WLAN 216 and UE 105 to one or more protocols usedby other elements of 5G CN 240 such as AMF 215. For example, N3IWF 250may support IPSec tunnel establishment with UE 105, termination ofIKEv2/IPSec protocols with UE 105, termination of N2 and N3 interfacesto 5G CN 240 for control plane and user plane, respectively, relaying ofuplink (UL) and downlink (DL) control plane Non-Access Stratum (NAS)signaling between UE 105 and AMF 215 across an N1 interface. In someother embodiments, WLAN 216 may connect directly to elements in 5G CN240 (e.g. AMF 215 as shown by the dashed line in FIG. 2 ) and not viaN3IWF 250. For example, direct connection of WLAN 216 to SGCN 240 mayoccur if WLAN 216 is a trusted WLAN for SGCN 240 and may be enabledusing a Trusted WLAN Interworking Function (TWIF) (not shown in FIG. 2 )which may be an element inside WLAN 216. It is noted that while only oneWLAN 216 is shown in FIG. 2 , some embodiments may include multipleWLANs 216.

Access nodes may comprise any of a variety of network entities enablingcommunication between the UE 105 and the AMF 215. This can include gNBs210, ng-eNB 214, WLAN 216, and/or other types of cellular base stations.However, access nodes (e.g., gNBs 210, ng-eNB 214, and/or WLAN 216)providing the functionality described herein may additionally oralternatively include entities enabling communications to any of avariety of RATs not illustrated in FIG. 2 , which may includenon-cellular technologies. Thus, the term “access node,” as used in theembodiments described herein below, may include but is not necessarilylimited to a gNB 210, ng-eNB 214 or WLAN 216.

In some embodiments, an access node, such as a gNB 210, ng-eNB 214, orWLAN 216 (alone or in combination with other components of the 5G NRpositioning system 200), may be configured to, in response to receivinga request for location information from the LMF 220, obtain locationmeasurements of uplink (UL) signals received from the UE 105) and/orobtain downlink (DL) location measurements from the UE 105 that wereobtained by UE 105 for DL signals received by UE 105 from one or moreaccess nodes. As noted, while FIG. 2 depicts access nodes configured tocommunicate according to 5G NR, LTE, and Wi-Fi communication protocols,respectively, access nodes configured to communicate according to othercommunication protocols may be used, such as, for example, a Node Busing a Wideband Code Division Multiple Access (WCDMA) protocol for aUniversal Mobile Telecommunications Service (UMTS) Terrestrial RadioAccess Network (UTRAN), an eNB using an LTE protocol for an EvolvedUTRAN (E-UTRAN), or a Bluetooth® beacon using a Bluetooth protocol for aWLAN. For example, in a 4G Evolved Packet System (EPS) providing LTEwireless access to UE 105, a RAN may comprise an E-UTRAN, which maycomprise base stations comprising eNBs supporting LTE wireless access. Acore network for EPS may comprise an Evolved Packet Core (EPC). An EPSmay then comprise an E-UTRAN plus an EPC, where the E-UTRAN correspondsto NG-RAN 235 and the EPC corresponds to SGCN 240 in FIG. 2 . Themethods and techniques described herein for obtaining a civic locationfor UE 105 may be applicable to such other networks.

The gNBs 210 and ng-eNB 214 can communicate with an AMF 215, which, forpositioning functionality, communicates with an LMF 220. The AMF 215 maysupport mobility of the UE 105, including cell change and handover of UE105 from an access node of a first RAT to an access node of a secondRAT. The AMF 215 may also participate in supporting a signalingconnection to the UE 105 and possibly data and voice bearers for the UE105. The LMF 220 may support positioning of the UE 105 using a CPlocation solution when UE 105 accesses the NG-RAN 235 or WLAN 216 andmay support position procedures and methods, including UE assisted/UEbased and/or network based procedures/methods, such as Assisted GNSS(A-GNSS), Observed Time Difference Of Arrival (OTDOA) (which may bereferred to in NR as Time Difference Of Arrival (TDOA)), Real TimeKinematic (RTK), Precise Point Positioning (PPP), Differential GNSS(DGNSS), Enhance Cell ID (ECID), angle of arrival (AoA), angle ofdeparture (AoD), WLAN positioning, round trip signal propagation delay(RTT), multi-cell RTT, and/or other positioning procedures and methods.The LMF 220 may also process location service requests for the UE 105,e.g., received from the AMF 215 or from the GMLC 225. The LMF 220 may beconnected to AMF 215 and/or to GMLC 225. In some embodiments, a networksuch as SGCN 240 may additionally or alternatively implement other typesof location-support modules, such as an Evolved Serving Mobile LocationCenter (E-SMLC) or a SUPL Location Platform (SLP). It is noted that insome embodiments, at least part of the positioning functionality(including determination of a UE 105's location) may be performed at theUE 105 (e.g., by measuring downlink PRS (DL-PRS) signals transmitted bywireless nodes such as gNBs 210, ng-eNB 214 and/or WLAN 216, and/orusing assistance data provided to the UE 105, e.g., by LMF 220).

The Gateway Mobile Location Center (GMLC) 225 may support a locationrequest for the UE 105 received from an external client 230 and mayforward such a location request to the AMF 215 for forwarding by the AMF215 to the LMF 220. A location response from the LMF 220 (e.g.,containing a location estimate for the UE 105) may be similarly returnedto the GMLC 225 either directly or via the AMF 215, and the GMLC 225 maythen return the location response (e.g., containing the locationestimate) to the external client 230.

A Network Exposure Function (NEF) 245 may be included in SGCN 240. TheNEF 245 may support secure exposure of capabilities and eventsconcerning SGCN 240 and UE 105 to the external client 230, which maythen be referred to as an Access Function (AF) and may enable secureprovision of information from external client 230 to 5GCN 240. NEF 245may be connected to AMF 215 and/or to GMLC 225 for the purposes ofobtaining a location (e.g. a civic location) of UE 105 and providing thelocation to external client 230.

As further illustrated in FIG. 2 , the LMF 220 may communicate with thegNBs 210 and/or with the ng-eNB 214 using an NR Positioning Protocolannex (NRPPa) as defined in 3GPP Technical Specification (TS) 38.445.NRPPa messages may be transferred between a gNB 210 and the LMF 220,and/or between an ng-eNB 214 and the LMF 220, via the AMF 215. Asfurther illustrated in FIG. 2 , LMF 220 and UE 105 may communicate usingan LTE Positioning Protocol (LPP) as defined in 3GPP TS 37.355. Here,LPP messages may be transferred between the UE 105 and the LMF 220 viathe AMF 215 and a serving gNB 210-1 or serving ng-eNB 214 for UE 105.For example, LPP messages may be transferred between the LMF 220 and theAMF 215 using messages for service-based operations (e.g., based on theHypertext Transfer Protocol (HTTP)) and may be transferred between theAMF 215 and the UE 105 using a 5G NAS protocol. The LPP protocol may beused to support positioning of UE 105 using UE assisted and/or UE basedposition methods such as A-GNSS, RTK, TDOA, multi-cell RTT, AoD, and/orECID. The NRPPa protocol may be used to support positioning of UE 105using network based position methods such as ECID, AoA, uplink TDOA(UL-TDOA) and/or may be used by LMF 220 to obtain location relatedinformation from gNBs 210 and/or ng-eNB 214, such as parameters definingDL-PRS transmission from gNBs 210 and/or ng-eNB 214.

In the case of UE 105 access to WLAN 216, LMF 220 may use NRPPa and/orLPP to obtain a location of UE 105 in a similar manner to that justdescribed for UE 105 access to a gNB 210 or ng-eNB 214. Thus, NRPPamessages may be transferred between a WLAN 216 and the LMF 220, via theAMF 215 and N3IWF 250 to support network-based positioning of UE 105and/or transfer of other location information from WLAN 216 to LMF 220.Alternatively, NRPPa messages may be transferred between N3IWF 250 andthe LMF 220, via the AMF 215, to support network-based positioning of UE105 based on location related information and/or location measurementsknown to or accessible to N3IWF 250 and transferred from N3IWF 250 toLMF 220 using NRPPa. Similarly, LPP and/or LPP messages may betransferred between the UE 105 and the LMF 220 via the AMF 215, N3IWF250, and serving WLAN 216 for UE 105 to support UE assisted or UE basedpositioning of UE 105 by LMF 220.

In a 5G NR positioning system 200, positioning methods can becategorized as being “UE assisted” or “UE based.” This may depend onwhere the request for determining the position of the UE 105 originated.If, for example, the request originated at the UE (e.g., from anapplication, or “app,” executed by the UE), the positioning method maybe categorized as being UE based. If, on the other hand, the requestoriginates from an external client or AF 230, LMF 220, or other deviceor service within the 5G network, the positioning method may becategorized as being UE assisted (or “network-based”).

With a UE-assisted position method, UE 105 may obtain locationmeasurements and send the measurements to a location server (e.g., LMF220) for computation of a location estimate for UE 105. ForRAT-dependent position methods location measurements may include one ormore of a Received Signal Strength Indicator (RSSI), Round Trip signalpropagation Time (RTT), Reference Signal Received Power (RSRP),Reference Signal Received Quality (RSRQ), Reference Signal TimeDifference (RSTD), Time of Arrival (TOA), AoA, Receive Time-TransmissionTime Difference (Rx-Tx), Differential AoA (DAoA), AoD, or Timing Advance(TA) for gNBs 210, ng-eNB 214, and/or one or more access points for WLAN216. Additionally or alternatively, similar measurements may be made ofsidelink signals transmitted by other UEs, which may serve as anchorpoints for positioning of the UE 105 if the positions of the other UEsare known. The location measurements may also or instead includemeasurements for RAT-independent positioning methods such as GNSS (e.g.,GNSS pseudorange, GNSS code phase, and/or GNSS carrier phase for GNSSsatellites 110), WLAN, etc.

With a UE-based position method, UE 105 may obtain location measurements(e.g., which may be the same as or similar to location measurements fora UE assisted position method) and may further compute a location of UE105 (e.g., with the help of assistance data received from a locationserver such as LMF 220, an SLP, or broadcast by gNBs 210, ng-eNB 214, orWLAN 216).

With a network based position method, one or more base stations (e.g.,gNBs 210 and/or ng-eNB 214), one or more APs (e.g., in WLAN 216), orN3IWF 250 may obtain location measurements (e.g., measurements of RSSI,RTT, RSRP, RSRQ, AoA, or TOA) for signals transmitted by UE 105, and/ormay receive measurements obtained by UE 105 or by an AP in WLAN 216 inthe case of N3IWF 250, and may send the measurements to a locationserver (e.g., LMF 220) for computation of a location estimate for UE105.

Positioning of the UE 105 also may be categorized as UL, DL, or DL-ULbased, depending on the types of signals used for positioning. If, forexample, positioning is based solely on signals received at the UE 105(e.g., from a base station or other UE), the positioning may becategorized as DL based. On the other hand, if positioning is basedsolely on signals transmitted by the UE 105 (which may be received by abase station or other UE, for example), the positioning may becategorized as UL based. Positioning that is DL-UL based includespositioning, such as RTT-based positioning, that is based on signalsthat are both transmitted and received by the UE 105. Sidelink(SL)-assisted positioning comprises signals communicated between the UE105 and one or more other UEs. According to some embodiments, UL, DL, orDL-UL positioning as described herein may be capable of using SLsignaling as a complement or replacement of SL, DL, or DL-UL signaling.

Depending on the type of positioning (e.g., UL, DL, or DL-UL based) thetypes of reference signals used can vary. For DL-based positioning, forexample, these signals may comprise PRS (e.g., DL-PRS transmitted bybase stations or SL-PRS transmitted by other UEs), which can be used forTDOA, AoD, and RTT measurements. Other reference signals that can beused for positioning (UL, DL, or DL-UL) may include Sounding ReferenceSignal (SRS), Channel State Information Reference Signal (CSI-RS),synchronization signals (e.g., synchronization signal block (SSB)Synchronizations Signal (SS)), Physical Uplink Control Channel (PUCCH),Physical Uplink Shared Channel (PUSCH), Physical Sidelink Shared Channel(PSSCH), Demodulation Reference Signal (DMRS), etc. Moreover, referencesignals may be transmitted in a Tx beam and/or received in an Rx beam(e.g., using beamforming techniques), which may impact angularmeasurements, such as AoD and/or AoA.

Antenna and Baseband Configurations

In order to detect the presence of multipath on received positioningsignals using existing antenna systems (e.g., UEs utilizing planarinverted F-shaped antenna (PIFA) components) and adjust according toembodiments described herein, the UE performs several actions: (1)Obtain positioning signals from one or more SVs. (2) Determine thedominant type of circular polarization of the positioning signals, i.e.,whether right-handed circularly polarized (RHCP) or left-handedcircularly polarized (LHCP). (3) Determine multipath based on the typeof circular polarization and/or other information. (4) Infer the type ofmultipath environment the UE is located based on the determination ofmultipath, and adjust performance settings to, e.g., improvepositioning.

In the subsequent discussions, various embodiments of an antennasubsystem and a baseband subsystem and their components will bedescribed with respect to FIGS. 3-11 . The antenna subsystem and thebaseband subsystem may be used to, e.g., obtain positioning signals anddetermine the multipath.

FIG. 3 illustrates a block diagram of a configuration of an antennasubsystem 310 and a baseband subsystem 320 of a wireless device (e.g., aUE 105 as described above and elsewhere herein), according to anembodiment. In some embodiments, the antenna subsystem 310 and basebandsubsystem 320 may be part of one or more transceivers configured totransmit and/or receive signals, including data signals and/orpositioning signals.

In a variety of embodiments, the antenna subsystem 310 may include aplurality of receiving antennas, such as two antennas 312-1 and 312-2(collectively referred to as antennas 312). In some embodiments, each ofthe antennas 312-1 and 312-2 may be configured to receive linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 312-1 and 312-2 may be a planar inverted-F antenna (PIFA)type antenna.

As an aside, circular polarization refers to a polarization state inwhich an electromagnetic wave (e.g., an RF signal) is rotating (orappears to be rotating) by virtue of two phase-shifted perpendicularelectromagnetic plane components, i.e., horizontal and verticalcomponents, propagating at a constant magnitude and rate. Circularlypolarized waves may have right-handed or left-handed polarization. RHCPsignals refer to signals encompassed by right-handed polarized waveswhose horizontal and vertical components are shifted by a 90-degreephase and whose vectors rotate clockwise relative to the direction ofpropagation of the wave. In contrast, LHCP signals are left-handed andhave horizontal and vertical components that are shifted by −90 degrees,and rotate counterclockwise relative to the direction of propagation.RHCP and LHCP signals are not necessarily purely RHCP or LHCP, and maycontain a dominant component.

One salient property of circularly polarized signals is that the“handedness” of the signal changes upon reflection from a surface. Theextent to which the handedness changes depends on various factors suchas the angle of incidence, type of material (e.g., opaqueness ortransparency), shape of the surface, etc. For reflection at normalincidence (i.e., perpendicular to a flat surface such that the reflectedwave returns back in the exact opposite direction), the polarizationreverses completely. For instance, a purely RHCP signal would becomecharacterized as purely LHCP. Practically speaking, signals wouldinteract with surfaces at angles of incidence that vary greatly, mayoccur more than once, and usually would not be at normal incidence.Reflection may further cause polarization to become more elliptical.Hence, positioning signals are typically received with a mixture ofpolarization state components, with partly right-handed polarization andpartly left-handed polarization. Often but not always, there is onedominant component, as will be discussed further with respect to FIG. 13.

If a circularly polarized positioning signal is transmitted from an SVwith a known “handedness,” detection of the handedness of the signal asreceived by an UE (thus indicating a change of handedness) may providean indication of the existence and/or type of multipath channelexperienced by the positioning signal as it travels from the SV to theUE. Positioning signals may also include data that support a positiondetermination process. Such data may include, but is not limited to, theposition of the SV, time of transmission, SV clock information, timeinformation (e.g., relationship to UTC), and SV health information. Withregard to the SV's position, this may be obtained in two forms: (i)so-called Almanac data, which provides a coarse, approximate position ofthe SV and (ii) so-called Ephemeris data, which provides a more preciseposition of the SV. The clocks of SV(s) (e.g., in a constellation) arehighly accurate and synchronized with each other and to absolute time,allowing determination of distance based on the position and timinginformation as noted above. The clock of the local receiver (e.g., UE105) is not synchronized to the SV(s), however, and the time of thelocal receiver clock and the unknown position of the receiver must bedetermined, e.g., using four SVs to derive a three-dimensional positionfor the receiver.

Referring back to FIG. 3 , in some embodiments, each of the antennas 312is configured to detect and receive RF signals of one type of linearpolarization. For example, antenna 312-1 may be a PIFA configured toreceive and/or detect signals or signal components having a verticalpolarization, and antenna 312-2 may be a PIFA configured to receiveand/or detect signals or signal components having a horizontalpolarization. That is, the antenna subsystem 310 may be configured todetect separate linear components of a circularly polarized signal.Hence, when the UE antenna subsystem 310 receives a circularly polarizedsignal (e.g., RHCP signals from a GNSS satellite), the UE does notrequire dedicated RHCP or LHCP antennas. A received circularly polarizedsignal detected as linear components may be “reconstructed” using an RFcoupler or combiner (as discussed below), and the UE 105 may thusadvantageously (cost- and space-effectively) utilize existing antennasthat are shared with other subsystems of the UE.

Depending on the multipath environment experienced by the receivedpositioning signal, the signal will include some combination ofright-handed (RHCP) component, left-handed (LHCP) component, and/orlinear component. Using an antenna configuration where each type ofpolarization of the positioning signal can be obtained, characteristics(e.g., signal strength) of the signal at each polarization may bemeasured, and thereby estimate the probability of multipath on thesignal. This information can then be used by a position determinationprocess to weight and de-weight the SVs and/or the signals accordinglyto yield a position result that is more accurate, precise, and reliablethan existing positioning, as will be discussed in more detail withrespect to FIG. 13 .

However, it will be recognized that, in certain embodiments, dedicatedantennas capable of detecting a particular circular polarization mayalternatively or additionally be used in the antenna subsystem 310. Forinstance, one of the antennas (e.g., 312-1) of the antenna subsystem 310may be configured to detect and receive RHCP signals, such aspositioning signals transmitted from one or more SVs (e.g., GNSSsatellites, noting that it is convention for GNSS satellites to emitRHCP positioning signals rather than LHCP positioning signals). Theother one of the antennas (e.g., 312-2) may be configured to detect andreceive left-hand circularly polarized (LHCP) signals. In theseembodiments, RF coupler 314 may not be necessary.

In some embodiments, more than two antennas may be employed in anycombination or fashion configured to receive linearly polarized, RHCPand/or LHCP signals. As but one example, a UE 105 may have threeantennas 312, where two of the antennas 312 are configured to receivevertical and horizontal signals, respectively, and one of the antennas312 is configured to receive RHCP signals. The RHCP antenna may beredundantly used to confirm the presence of RHCP signals for use casesrequiring positioning accuracy and precision, e.g., drone navigation. Inanother embodiment, an antenna 312 may be configured to receiveelliptically polarized signals. In another embodiment, a UE 105 may havemultiple antenna subsystems each having one or more antennas.

The antenna subsystem 310 may include an RF coupler 314 that isconfigured to receive and combine inputs from the two antennas 312 intoan output signal having a different polarization type. In someembodiments, the RF coupler 314 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals. Forexample, linearly polarized components obtained via the antennas 312 maybe combined into circularly polarized signals, e.g., RHCP or LHCPsignals.

The antenna subsystem 310 may further include a switch 316 that receivesand transmits one type of circularly polarized signal at a time. Theoutput of the RF coupler 314 may be transmitted to and received by theswitch 316. In one embodiment, the RF coupler 314 may include a switchin lieu of a separate switch (e.g., 316). The switch 316 may be toggledbased on control signals 317. In some embodiments, the basebandsubsystem 320 may generate the control signals 317 (and control signals325, synchronized with control signals 317). In some embodiments, theswitch 316 may be toggled at a constant rate (e.g., every 10 ms, 100 ms,500 ms, etc. based on control signals 317) so as to sample signals ofdifferent types (i.e., RHCP or LHCP) output from the RF coupler 314 overa defined time period. Put another way, both types of circularlypolarized signals may be received by “time-multiplexing” with the switch316, receiving for example RHCP signals half of the time on a regularinterval (e.g., every other 10 ms) and LHCP signals half of the time ona regular interval (e.g., every other 10 ms) as the switch repeatedlytoggles between the two positions at the constant rate. In some cases,the switch may be toggled at a non-constant rate so as to sample somesignals, e.g., RHCP signals, more often. An illustrative graph 330 showsthat some time periods are occupied by RHCP signals and other timeperiods are occupied by LHCP signals in, e.g., a 1:1 ratio duringtransmission over a signal path 318.

The antenna subsystem 310 may be configured for signal communicationwith the baseband subsystem 320 and/or its components via the signalpath 318. In some embodiments, the signal path 318 may be a shieldedanalog signal path, e.g., a coaxial cable, a signal trace in proximityto guard traces, a shunt trace.

The switching performed by the switch 316 may advantageously reduce thecomplexity of the architecture as shown in FIG. 3 , including the signalpath 318 connecting the antenna subsystem 310 and the baseband subsystem320. More specifically, only a single signal path may be needed by usinga switch, as opposed to multiple signal paths for respective signals(e.g., RHCP and LHCP). Note that in certain embodiments, other signalpaths and/or buses may be present for delivering received signals ordata for purposes other than positioning.

In one implementation, the switch 316 may be configured to selectivelypass signals of a certain type (e.g., RHCP signals) while rejectingother signals until indicated otherwise (e.g., toggled by a controlsignal) by the antenna subsystem 310 or the baseband subsystem 320. Forexample, the baseband subsystem 320 may desire to receive RHCP signals(or RHCP-dominated signals) only and toggle the switch 316 to onlyreceive RHCP signals while rejecting LHCP signals.

In another implementation, activity of the antennas may be adjusted inUEs using dedicated RHCP and LHCP antennas. For example, one of theantennas 312 may remain active in order to detect and receive RHCPsignals only, and the other antenna is deactivated to disregard any LHCPsignals. In configurations with more than two antennas, redundantantennas may be similarly deactivated.

While the antenna subsystem 310 is comprised primarily of hardware andcircuitry configured to receive and generate signals of differentpolarization states, the baseband subsystem 320 is comprised primarilyof hardware and circuitry configured to process signals obtained fromthe antenna subsystem. In some embodiments, the baseband subsystem 320may include one or more receivers, such as RF receiver modules 322-1,322-2 (collectively referred to as receivers 322). Although FIG. 3illustrates two receivers 322-1 and 322-2, it is appreciated that insome embodiments, a baseband subsystem 320 may include and operate asingle receiver (e.g., 322-1); and in some embodiments, a two-receiversubsystem as shown in FIG. 3 may have one receiver idle depending on thestate of the switch 316 and/or switch 324 (based, e.g., on controlsignals 317 and/or 325). In some embodiments, the baseband subsystem 320may include at least one processor and/or logic circuitry. The receivers322 may demodulate received RHCP signals so as to obtain data containedin the positioning signals (e.g., positioning and timing information asalluded to above). In certain embodiments, signals of a givenpolarization state may be processed (e.g., demodulated) by acorresponding receiver. For instance, RHCP signals may be processed byreceiver 322-1, and LHCP signals may be processed by receiver 322-2. Inaddition, each receiver 322 may measure a signal strength of thereceived signal. The strength of these signals may be measured andrepresented by their carrier-to-noise-density ratio C/N₀, which is theratio of carrier power C to noise power density N₀. These signalstrengths may be generated as data or data structures (e.g., tables orreports containing C/N₀ values for RHCP and LHCP signals over definedsampling time periods) and accessed by other components of the UE (e.g.,processor, memory) for evaluation or storage. As part of the evaluation,various statistical parameters may be obtained from the C/N₀ values,e.g., mean (over a given set of values), average (over the runningtotal), median, minimum, maximum, and/or standard deviation.

The baseb and subsystem 320 may further include a switch 324. Similar tothe switch 316 in the antenna subsystem 310, the switch 324 in thebaseband subsystem 320 may toggle at a constant rate. The switch 324 maybe toggled based on control signals 325 generated at the basebandsubsystem 320. Both switches 316 and 324 may toggle synchronously at thesame rate so as to allow proper routing of the received RHCP or LHCPsignals to the respective receivers 322-1 and 322-2.

In some embodiments, switches 316 and 324 may be set to receive LHCPoutputs to obtain sample measurements based on certain triggeringconditions, and then brought back to RHCP for the final positionsolution. In these embodiments, the switch is normally set to receiveRHCP signals, and receiving LHCP signals may not be desired for longperiods of time. However, in some implementations, the switch may betriggered to be set to receive LHCP signals periodically (every 10seconds, 15 seconds, 60 seconds, etc.) for a portion of that period (for3 seconds, 5 seconds, 15 seconds, etc.). In some implementations, theswitch may be triggered to be set to receive LHCP signals based on datawithin the receivers 322. For example, one or more of the receivers 322may detect C/N₀ variations or measurement residual values from theestimated position from prior measurements, leading to a suspicion orindication of multipath on at least one SV. As another example, thereceivers 322 may also have suspicion or indication of a multipath-richenvironment (e.g., an urban canyon or indoors) based on, e.g., priormeasurements, “crowdsourced” data stored and accessible by the UE (aswill be discussed in greater detail below), or positioning based onother communication protocols (e.g., WLAN or cellular) that may indicatethat a UE is in a certain known area. Under such conditions, thereceivers 322 may switch momentarily to LHCP, obtain a measurement, thenswitch back to RHCP, obtain another measurement, and from the differencein RHCP and LHCP measurements, determine which SV(s) have a likelihoodof being corrupted by multipath, and de-weight them in the finalposition solution. Specific examples of comparison of RHCP and LHCPsignal components to determine multipath will be described further withrespect to FIG. 13 .

It is useful for a UE to have the capability to obtain and identifycircularly polarized signals via linear antennas as shown in FIG. 3 .Specifically, by employing linear antennas and a baseband subsystem thatcan obtain circularly polarized RHCP or LHCP signals, circularpolarization characteristics of a positioning signal may be measuredwithout use of dedicated circularly polarized antennas, and therebyallow determination or estimation of multipath or probability ofmultipath on the signal using existing antennas (e.g., PIFA) on the UE.Specifically, RHCP and LHCP signal strengths may be compared to eachother to deduce the presence of multipath or the likelihood ofmultipath. Although not entirely determinative of signaling quality,such multipath determination can provide another dimension to existingpositioning techniques to optimize the positioning of a device.

Further, this type of approach may be used to characterize or classifythe type of environment the UE is in (open field, urban canyon,suburban, etc.), and use the type of environment to tune or adjust thebehavior of the device, e.g., adjust sensitivity threshold for signalreception or energy detection, adjust the frequency band and/orreallocate resources for antenna usage (e.g., seek Wi-Fi signalsinstead), adjust “backoff” periods for detecting positioning signals, orreduce processing or battery usage. This can be especially helpful if ithas been determined that the UE is in an “urban canyon” environment witha high likelihood of multipath caused by numerous buildings orstructures.

Such multipath information and type of environment inferred fromcomparing RHCP and LHCP signal strengths can also drive variousoperational decisions. The information based on multipath determinationcan be used to, e.g., weight, de-weight, or reject one or more SVsand/or their signals to yield a position result that is more reliablethan traditional positioning. Such improved positioning may be useful insituations where WLAN or cellular communication is unavailable to assistthe UE with positioning.

Moreover, in certain embodiments, multipath information obtained in themanner described herein may be helpful for identifying UE locations andenvironments where there is no prior tracking history. That is,characterization of an environment that the UE has previously measuredits location in may be used to supplement or obviate usage of at leastsome positioning techniques. For example, if it is known (from priormeasurement or prior “crowdsourced” data stored on or accessible via theUE) that a particular intersection in a city tends to yield a specificpolarization profile or behavior (e.g., measurements RHCP and LHCPsignal components resulting from multipath caused by surroundingbuildings), the UE may, for instance, match the polarization profile toknown locations and other environmental contexts (e.g., buildings,tunnels, natural or geographic features), and thereby estimate itsposition without necessarily relying on trilateration, signal strengthmeasurement, etc. Moreover, in some implementations, machine learningtechniques (using, e.g., neural networks) may also be used with theprior crowdsourced data to train the UE or portions of the positioningsystem (e.g., the location server 160) to yield more accurate orgranular relationships between polarization profiles, multipathdetermination, and classifications of the environmental context. In someimplementations, a learning model may be continually trained (using atleast, e.g., forward propagation and backpropagation) utilizing anysuitable supervised, unsupervised, semi-supervised, and/or reinforcedlearning algorithms in conjunction with the prior data. Polarizationprofiles correlating signal strengths, multipath determination, andenvironment types are further discussed below with respect to FIG. 13 .

Hence, the configuration of FIG. 3 is capable of using linear antennas312 to obtain signals having specific circular polarizations, i.e., RHCPand LHCP. A comparison of the strengths of the RHCP and LHCP componentsof the received signal may be used to make a determination of themultipath environment, or the probability of multipath, experienced bythe positioning signal from a specific SV (i.e., on a per-SV basis).

FIG. 4 illustrates a block diagram of a configuration of an antennasubsystem 410 and a baseband subsystem 420 of a wireless device (e.g., aUE 105), according to another embodiment. The antenna subsystem 410 mayinclude a plurality of receiving antennas, such as two antennas 412-1and 412-2 (collectively referred to as antennas 412). In someembodiments, each of the antennas 412-1 and 412-2 may be configured todetect linearly polarized signals or signal components. In certainembodiments, each of the antennas 412-1 and 412-2 may be a planarinverted-F antenna (PIFA) type antenna. Antennas 412 may be examples ofthe antennas 312 discussed with respect to FIG. 3 .

The antenna subsystem 410 may include an RF coupler 414 that isconfigured to receive and combine inputs from the two antennas 412 intoan output signal having a different polarization type. In someembodiments, antennas 412 may include dedicated RHCP and LHCP antennas.In these embodiments, RF coupler 414 may not be necessary. In someembodiments, the RF coupler 414 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals, e.g.,RHCP and LHCP signals. For example, linearly polarized componentsobtained via the antennas 412 may be combined into circularly polarizedsignals, e.g., RHCP or LHCP signals.

The antenna subsystem 410 may be configured for signal communicationwith the baseband subsystem 420 and/or its components via two (or more)signal paths 418-1 and 418-2 (collectively referred to as signal paths418). In some embodiments, signal paths 418 may be shielded analogsignal paths, e.g., coaxial cables, signal traces in proximity to guardtraces, shunt traces. One type of output from the RF coupler 414, e.g.,RHCP signals, may be transmitted directly to a receiver module 422-1 ofthe baseband subsystem 420 via the signal path 418-1. Another type ofoutput from the RF coupler 414, e.g., LHCP signals, may be transmitteddirectly to a receiver module 422-2 of the baseband subsystem 420 viathe signal path 418-2. Receiver modules 422-1 and 422-2 (collectivelyreferred to as 422) may be examples of receivers 322-1 and 322-2 of FIG.3 . Similar to embodiments described with respect to FIG. 3 , in certainembodiments, the baseband subsystem 420 may include and operate a singlereceiver (e.g., 422-1), with RHCP signals and LHCP signalstime-multiplexed over one signal path.

The configuration of FIG. 4 differs from that of FIG. 3 , as it includesmultiple signal paths but does not include switches such as switches 316and 324. No on-demand real-time switching is required since the RHCP andLHCP signals are available to the baseband circuitry simultaneously.Advantageously, the receivers 422 may each receive an increased amountof data as compared to the receivers 322-1 and 322-2 of FIG. 3 becausethe toggling of switches 316 and 324 causes the receivers 322 to sampleless than the full amount of each type of signal over a given period oftime in a “time-multiplexed” fashion, and the receivers 422 receive allof the output signals. Illustrative graphs 430-1 and 430-2 show that theentire transmission period for the signal path 418-1 is occupied by RHCPsignals and the entire transmission period for the signal path 418-2 isoccupied by LHCP signals.

However, the UE may be space-constrained depending on its form factor,chassis type, or device capabilities requiring additional or largercomponents. For instance, UEs dedicated to positioning (e.g., GPSequipment) may benefit from dedicated signal paths 418, while small formfactor consumer devices such as smartphones may not. Moreover, it isstill possible that the baseband subsystem 420 may choose to processonly RHCP or LHCP signals at any given time based on limited orre-routed processing resources. Thus, utilizing multiple signal paths418 over a switch (e.g., 316) may be desirable depending on theimplementation.

FIG. 5 is a block diagram of a configuration of an antenna subsystem 510and a baseband subsystem 520 of a wireless device (e.g., a UE 105),according to another embodiment. The antenna subsystem 510 may include aplurality of receiving antennas, such as two antennas 512-1 and 512-2(collectively referred to as antennas 512). In some embodiments, each ofthe antennas 512-1 and 512-2 may be configured to receive linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 512-1 and 512-2 may be a planar inverted-F antenna (PIFA)type antenna. Antennas 512 may be examples of the antennas 312 discussedwith respect to FIG. 3 .

The antenna subsystem 510 may include an RF coupler 514 that isconfigured to receive and combine inputs from the two antennas 512 intoan output signal having a different polarization type. In someembodiments, the RF coupler 514 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals, e.g.,RHCP and LHCP signals. For example, linearly polarized componentsobtained via the antennas 512 may be combined into circularly polarizedsignals, e.g., RHCP or LHCP signals.

In some embodiments, the antenna subsystem 510 may include an oscillatorcircuit 532, a multiplier circuit 534, a filter circuit 535, and anadder circuit 536. The oscillator 532 may be configured to produce analternating waveform (e.g., a sin wave) of a prescribed frequency. Themultiplier 534 may be configured to shift the frequency of one of theoutputs of the RF coupler 514, e.g., the LHCP signals, away from thebaseband by applying the waveform generated by the oscillator 532 to theoutput of the RF coupler. The filter 535 may be configured to filter thefrequency portion of interest, and in some embodiments may include,e.g., a bandpass filter. The adder 536 may be configured to combine thesignal waveforms of one output (e.g., RHCP signals) with the signalwaveforms of another output (e.g., LHCP signals) modulated to adifferent frequency domain by the multiplier 534 to produce afrequency-multiplexed signal. In some embodiments, a frequency shiftercomponent (not shown) may include at least the oscillator, themultiplier, and/or the filter.

The antenna subsystem 510 may be configured for signal communicationwith the baseband subsystem 520 and/or its components via the signalpath 518. In some embodiments, the signal path 518 may be a shieldedanalog signal path, e.g., a coaxial cable, a signal trace in proximityto guard traces, a shunt trace. A single signal path (e.g., 518) maycarry the frequency-multiplexed signal from the adder 536 to thebaseband subsystem 520.

The baseband subsystem 520 may include a diplexer 538, configured tosplit the frequency-multiplexed signal received over the signal path518. Each split signal may experience some insertion loss. The basebandsubsystem 520 may further include one or more receivers, such as RFreceiver modules 522-1, 522-2 (collectively referred to as receivers522). Receiver modules 522-1 and 522-2 may be examples of receivers322-1 and 322-2 of FIG. 3 . More specifically, receiver module 522-1 maybe configured to receive and demodulate baseband RHCP signals. Receivermodule 522-2 may be configured to receive and demodulate baseband LHCPsignals. Hence, receiver module 522-1 does not require any shifting todemodulate RHCP signals in the received frequency-multiplexed signalsince RHCP signals have not been shifted, and receiver module 522-2requires downshifting of the LHCP signals.

To that end, the baseband subsystem 520 may include an oscillatorcircuit 540, a multiplier circuit 542, and a filter circuit 544. Theoscillator 540 may be configured to produce an alternating waveform(e.g., a sin wave) of a prescribed frequency similar to that of thefrequency of the waveform generated by oscillator 532. The multiplier542 may apply the waveform to the received signal to downshift thefrequency of the LHCP signals in the frequency-multiplexed signal backto the original frequency range. The filter 544 may be configured tofilter the frequency portion of interest, and in some embodiments mayinclude, e.g., a low pass filter.

Similar to the time-multiplexing embodiment of FIG. 3 , theconfiguration of FIG. 5 does not require multiple signal paths. Anillustrative graph 530 shows that at least one frequency range isoccupied by RHCP signals and at least another frequency range isoccupied by LHCP signals, both of which may be sampled at the antennasubsystem 510 and transmitted over the single signal path 518 during theentire transmission period. The reconstruction of circularly polarizedsignals according to the FIG. 5 embodiment requires multipletransformations via the RF coupler 514, oscillator 532, diplexer 538,and oscillator 540, among other components, which may result in loss ofsignal power while adding costs (e.g., battery power, component costs)to operate. However, this configuration may result in fewer wiring andless electromagnetic interference.

FIG. 6 is a block diagram of a configuration of an antenna subsystem 610and a baseband subsystem 620 of a wireless device (e.g., a UE 105),according to another embodiment. The antenna subsystem 610 may include aplurality of receiving antennas, such as two antennas 612-1 and 612-2(collectively referred to as antennas 612). In some embodiments, each ofthe antennas 612-1 and 612-2 may be configured to detect linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 612-1 and 612-2 may be a planar inverted-F antenna (PIFA)type antenna. Antennas 612 may be examples of the antennas 312 discussedwith respect to FIG. 3 .

The antenna subsystem 610 may include an RF coupler 614 that isconfigured to receive and combine inputs from the two antennas 612 intoan output signal having a different polarization type. In someembodiments, the RF coupler 614 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals, e.g.,RHCP and LHCP signals. For example, linearly polarized componentsobtained via the antennas 612 may be combined into circularly polarizedsignals, e.g., RHCP or LHCP signals.

The antenna subsystem 610 may include a corresponding quantizer 640-1 or640-2 (collectively referred to as quantizers 640) for each output ofthe RF coupler 614. In some embodiments, each quantizer 640 may be ananalog-to-digital converters (ADC), configured to convert analog signalsinto digital signals. For example, RHCP signals may be input to the ADC640-1, and LHCP signals may be input to the ADC 640-2, resulting indigital signals (i.e., bits) as outputs.

The antenna subsystem 610 may be configured for digital datacommunication with the baseband subsystem 620 and/or its components viatwo (or more) data buses 618-1 and 618-2 (collectively referred to asbuses 618). In some embodiments, buses 618 may include any type ofcommunication cables, lines, wires, links, pins, used with any knownarchitecture (Serial ATA (SATA), Peripheral Component Interconnect(PCI), etc.). The buses 618 may also include a coaxial cable such as thesignal path 318 used with the FIG. 3 embodiment.

The output from the ADC 640-1 may be transmitted directly to a receivermodule 622-1 of the baseband subsystem 620 via the data bus 618-1. Theoutput from the ADC 640-2 may be transmitted directly to a receivermodule 622-2 of the baseband subsystem 620 via the data bus 618-2.Receiver modules 622-1 and 622-2 (collectively referred to as 622) maybe configured to receive digitized data and perform similar functions asthose of receivers 322-1 and 322-2 of FIG. 3 (including, e.g.,determining C/No values). Receivers 622 may also determine and quantizesignal strength levels based on the received digital data from theantenna subsystem 610. For example, signal strengths may be assigned oneof, e.g., 256 discrete levels represented by 8 bits. This range ofvalues may allow efficient statistical binning (e.g., in a histogram)and derivation of other statistical parameters as noted elsewhereherein.

Using multiple data buses may allow increased throughput of datatransferred between the antenna subsystem 610 and the baseband subsystem620, as compared to using signal paths. Illustrative graphs 630-1 and630-2 show that the entire transmission period for the data bus 618-1 isoccupied by RHCP signals and the entire transmission period for the databus 618-2 is occupied by LHCP signals. In positioning-intensiveapplications of the UE (e.g., navigation, travel, gaming, UE as adedicated GPS system), inclusion of additional components in the UE suchas quantizers (e.g., 640) and data buses (e.g., 618) may advantageouslyspeed up location determination.

FIG. 7 is a block diagram of a configuration of an antenna subsystem 710and a baseband subsystem 720 of a wireless device (e.g., a UE 105),according to another embodiment. The antenna subsystem 710 may include aplurality of receiving antennas, such as two antennas 712-1 and 712-2(collectively referred to as antennas 712). In some embodiments, each ofthe antennas 712-1 and 712-2 may be configured to detect linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 712-1 and 712-2 may be a planar inverted-F antenna (PIFA)type antenna. Antennas 712 may be examples of the antennas 312 discussedwith respect to FIG. 3 .

The antenna subsystem 710 may include an RF coupler 714 that isconfigured to receive and combine inputs from the two antennas 712 intoan output signal having a different polarization type. In someembodiments, the RF coupler 714 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals, e.g.,RHCP and LHCP signals. For example, linearly polarized componentsobtained via the antennas 712 may be combined into circularly polarizedsignals, e.g., RHCP or LHCP signals.

The antenna subsystem 710 may include a corresponding quantizer 740-1 or740-2 (collectively referred to as quantizers 740) for each output ofthe RF coupler 714. In some embodiments, each quantizer 740 may be ananalog-to-digital converters (ADC), configured to convert analog signalsinto digital signals. For example, RHCP signals may be input to the ADC740-1, and LHCP signals may be input to the ADC 740-2, resulting indigital signals (i.e., bits) as outputs. Quantizers 740 may be examplesof the quantizers discussed with respect to FIG. 6 .

The antenna subsystem 710 may also include a digital combiner 742,configured to combine multiple digital signals into one signal. Oncequantized into digital form, the RHCP and LHCP signals can be combinedin a myriad of ways and transmitted over a path 718 from the antennasubsystem 710 to the baseband subsystem 720. Here, a combiner 742generally represents such an operation. For example, if the path 718 isa data line or bus having sufficiently high data rate, the combiner 742can simply be implemented as a multiplexer that multiplexes thedigitized RHCP and LHCP signals into one digital stream, which can betransmitted over the path 718. Path 718 may be an example of the databus 618 of FIG. 6 .

In some embodiments, the digital combiner 742 may include or be coupledto a switch (not shown) such that the signals from the quantizers 740are time-multiplexed. The switch may be toggled at a constant rate, andmay be an example of the switch 316 discussed with respect to FIG. 3 .An illustrative graph 730 shows that some time periods are occupied byconverted RHCP signals and other time periods are occupied by convertedLHCP signals in, e.g., a 1:1 ratio during transmission over the path718.

The baseband subsystem 720 may include a digital splitter 744, whichreverses the combination performed by the digital combiner 742. In someembodiments, the digital splitter 744 may include another switch (notshown), which may be toggled synchronously at the same rate as theswitch associated with the digital combiner 742 so as to allow properrouting of the converted RHCP and LHCP signals to respective receivers722-1 and 722-2 (collectively referred to as receivers 722). Thereceivers 722 may be configured to receive digitized data and performsimilar functions as those of receivers 322-1 and 322-2 of FIG. 3(including, e.g., determining C/N₀ values). Receivers 722 may alsodetermine and quantize signal strength levels based on the receiveddigital data from the antenna subsystem 710. Although additionalcomponents such as the digital combiner 742 and digital splitter 744 maycause signal power loss, this configuration may result in fewer wiringand less electromagnetic interference, which may be advantageous forcertain smaller form factor UEs.

FIG. 8 is a block diagram of a configuration of an antenna subsystem 810and a baseband subsystem 820 of a wireless device (e.g., a UE 108),according to another embodiment. The antenna subsystem 810 may include aplurality of receiving antennas, such as two antennas 812-1 and 812-2(collectively referred to as antennas 812). In some embodiments, each ofthe antennas 812-1 and 812-2 may be configured to detect linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 812-1 and 812-2 may be a planar inverted-F antenna (PIFA)type antenna. Antennas 812 may be examples of the antennas 312 discussedwith respect to FIG. 3 .

The antenna subsystem 810 may be configured for signal communicationwith the baseband subsystem 820 and/or its components via two (or more)signal paths 818-1 and 818-2 (collectively referred to as signal paths818). In some embodiments, signal paths 818 may be shielded analogsignal paths, e.g., coaxial cables, signal traces in proximity to guardtraces, shunt traces.

The baseband subsystem 820 may include an RF coupler 824 that isconfigured to receive and combine inputs from the two antennas 812 intoan output signal having a different polarization type. In someembodiments, the RF coupler 824 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., linearly verticallypolarized (LV) and linearly horizontally polarized (LH)) and outputcombined phase-shifted signals, e.g., RHCP and LHCP signals. Forexample, linearly polarized components obtained via the antennas 812 maybe combined into circularly polarized signals, e.g., RHCP or LHCPsignals.

Resulting RHCP signals output from the RF coupler 824 may be receivedand processed by a corresponding receiver module 822-1, and LHCP outputsignals from the RF coupler 824 may be received and processed by acorresponding receiver module 822-2. To this end, signals received atantenna 812-1 may be directly transmitted to the coupler 824 via thesignal path 818-1, and signals received at antenna 812-2 may be directlytransmitted to the coupler 824 via the signal path 818-2. Receivermodules 822-1 and 822-2 (collectively referred to as receivers 822) maybe examples of receivers 322-1 and 322-2 of FIG. 3 .

In contrast to the embodiment shown in FIG. 4 , the signals are combinedat the baseband subsystem 820 rather than at the antenna subsystem 810in the embodiment of FIG. 8 . Similar advantages and tradeoffs exist inthe FIG. 8 embodiment; i.e., each type of signal is received at thecorresponding receiver for the entire duration of transmission over thecorresponding one of multiple signal paths. Wireless devices or systemsutilizing more robust baseband subsystems (e.g., those capable ofreceiving and transmitting, selectively or otherwise, various types ofwireless signals, including WLAN, cellular, GNSS positioning, Bluetooth,etc.) may include an RF coupler (e.g., 824) for use with such purposesor related considerations. Linearly polarized signals may be received bythe baseband subsystem 820 and/or routed elsewhere (e.g., cellularcomponents) instead of being preemptively combined at the antennasubsystem. Illustrative graphs 830-1 and 830-2 show that the entiretransmission period for the signal path 818-1 is occupied by linearlyvertical signals and the entire transmission period for the signal path818-2 is occupied by linearly horizontal signals.

FIG. 9 is a block diagram of a configuration of an antenna subsystem 910and a baseband subsystem 920 of a wireless device (e.g., a UE 105),according to another embodiment. The antenna subsystem 910 may include aplurality of receiving antennas, such as two antennas 912-1 and 912-2(collectively referred to as antennas 912). In some embodiments, each ofthe antennas 912-1 and 912-2 may be configured to receive linearlypolarized signals or signal components. In certain embodiments, each ofthe antennas 912-1 and 912-2 may be a planar inverted-F antenna (PIFA)type antenna. Antennas 912 may be examples of the antennas 312 discussedwith respect to FIG. 3 .

In some embodiments, the antenna subsystem 910 may include an oscillatorcircuit 932, a multiplier circuit 934, a filter circuit 935, and anadder circuit 936, which may be examples of the oscillator circuit 532,multiplier circuit 534, filter circuit 535, and adder circuit 536 asdescribed with respect to FIG. 5 . Here, the multiplier 934 may beconfigured to shift the frequency of one of the received linearlypolarized signals, e.g., the horizontally polarized signals as shown inFIG. 9 , away from the baseband by applying the waveform generated bythe oscillator 932. It will be appreciated that in other embodiments,the vertically polarized signals may be shifted instead. The adder 936may be configured to combine the signal waveforms of one output (e.g.,vertically polarized signals) with the signal waveforms of anotheroutput (e.g., horizontally polarized signals) modulated to a differentfrequency domain by the multiplier 934 to produce afrequency-multiplexed signal. In some embodiments, a frequency shiftercomponent (not shown) may include at least the oscillator, themultiplier, and/or the filter.

The antenna subsystem 910 may be configured for signal communicationwith the baseband subsystem 920 and/or its components via the signalpath 918. The signal path 918 may be an example of the signal path 518of FIG. 5 . A single signal path (e.g., 918) may carry thefrequency-multiplexed signal from the adder 936 to the basebandsubsystem 920.

The baseband subsystem 920 may include a diplexer 938, configured tosplit the frequency-multiplexed signal received over the signal path918. The diplexer 938 may be an example of the diplexer 538 of FIG. 5 .The baseband subsystem 920 may further include an oscillator circuit940, a multiplier circuit 942, and a filter circuit 944, which may beexamples of the oscillator circuit 540, multiplier circuit 542, andfilter circuit 544 of FIG. 5 . The multiplier 942 may apply frequencyshifting of the received signal to downshift the frequency of thehorizontally polarized signals in the frequency-multiplexed signal backto the original frequency range.

The baseband subsystem 920 may further include an RF coupler 914 that isconfigured to receive and combine inputs from the splitter 938 intooutput signals having different circularly polarized types. In someembodiments, the RF coupler 914 may be a 90-degree hybrid coupler,configured to receive two input signals (e.g., vertically polarized andhorizontally polarized) and output combined phase-shifted signals, e.g.,RHCP and LHCP signals. For example, linearly polarized componentsobtained via the antennas 912, shifted at the antenna subsystem 910, andrecovered at the baseband subsystem 920 may be combined into circularlypolarized signals, e.g., RHCP or LHCP signals. RHCP and LHCP signals maybe received at one or more receivers, such as RF receiver modules 922-1,922-2. Receiver modules 922-1 and 922-2 may be examples of receivers522-1 and 522-2 of FIG. 5 .

In this manner, linearly polarized signals may be frequency-multiplexedand received over a single signal path, similar to FIG. 5 . Anillustrative graph 930 shows that at least one frequency range isoccupied by linearly vertical (LV) signals and at least anotherfrequency range is occupied by LH (linearly horizontal) signals.

FIG. 10 is a block diagram of a configuration of an antenna subsystem1010 and a baseband subsystem 1020 of a wireless device (e.g., a UE105), according to another embodiment. The antenna subsystem 1010 mayinclude a plurality of receiving antennas, such as two antennas 1012-1and 1012-2 (collectively referred to as antennas 1012). In someembodiments, each of the antennas 1012-1 and 1012-2 may be configured toreceive linearly polarized signals or signal components. In certainembodiments, each of the antennas 1012-1 and 1012-2 may be a planarinverted-F antenna (PIFA) type antenna. Antennas 1012 may be examples ofthe antennas 312 discussed with respect to FIG. 3 .

The antenna subsystem 1010 may include quantizers 1040-1 and 1040-2(collectively referred to as quantizers 1040) for antennas 1012. In someembodiments, each quantizer 1040 may be an analog-to-digital converters(ADC), configured to convert analog signals into digital signals, andmay be an example of a quantizer 640 of FIG. 6 . In some embodiments,each ADC 1040 may be configured to convert linearly polarized signalsreceived by antennas 1012.

The antenna subsystem 1010 may be configured for digital datacommunication with the baseband subsystem 1020 and/or its components viatwo (or more) data buses 1018-1 and 1018-2 (collectively referred to asbuses 1018), which may be examples of data buses 618-1 and 618-2 of FIG.6 .

The baseband subsystem 1020 may include an RF coupler 1014 that isconfigured to receive and combine inputs from the two antennas 1012. Tothis end, outputs from ADCs 1040 may be transmitted directly to the RFcoupler 1014. In some embodiments, the RF coupler 1014 may be a90-degree hybrid coupler, configured to receive two input signals (e.g.,vertically polarized and horizontally polarized) and output combinedphase-shifted signals, e.g., RHCP and LHCP signals. For example,digitized linearly polarized signals received from the antenna subsystem1020 may be combined into circularly polarized signals, e.g., RHCP orLHCP signals. RHCP and LHCP signals may be received at one or morereceivers, such as RF receiver modules 1022-1, 1022-2. Receiver modules1022-1 and 1022-2 may be examples of receivers 622-1 and 622-2 of FIG. 6.

Using multiple data buses may allow increased throughput of datatransferred between the antenna subsystem 1010 and the basebandsubsystem 1020, as compared to using signal paths. Illustrative graphs1030-1 and 1030-2 show that the entire transmission period for the databus 1018-1 is occupied by LV signals and the entire transmission periodfor the data bus 1018-2 is occupied by LH signals.

FIG. 11 is a block diagram of a configuration of an antenna subsystem1110 and a baseband subsystem 1120 of a wireless device (e.g., a UE105), according to another embodiment. The antenna subsystem 1110 mayinclude a plurality of receiving antennas, such as two antennas 1112-1and 1112-2 (collectively referred to as antennas 1112). In someembodiments, each of the antennas 1112-1 and 1112-2 may be configured todetect linearly polarized signals or signal components. In certainembodiments, each of the antennas 1112-1 and 1112-2 may be a planarinverted-F antenna (PIFA) type antenna. Antennas 1112 may be examples ofthe antennas 312 discussed with respect to FIG. 3 .

The antenna subsystem 1110 may include quantizers 1140-1 and 1140-2(collectively referred to as quantizers 1140) for antennas 1112. In someembodiments, each quantizer 1140 may be an analog-to-digital converters(ADC), configured to convert analog signals into digital signals, andmay be an example of a quantizer 740 of FIG. 7 . In some embodiments,each ADC 1140 may be configured to convert linearly polarized signalsreceived by antennas 1112.

The antenna subsystem 1110 may also include a digital combiner 1142,configured to combine multiple digital signals into one signal. Oncequantized into digital form, the LV and LH signals can be combined in amyriad of ways and transmitted over a path 1118 from the antennasubsystem 1110 to the baseband subsystem 1120. Here, a combiner 1142generally represents such an operation. For example, if the path 1118 isa data line or bus having sufficiently high data rate, the combiner 1142can simply be implemented as a multiplexer that multiplexes thedigitized LV and LH signals into one digital stream, which can betransmitted over the path 1118.

In some embodiments, the digital combiner 1142 may include or be coupledto a switch (not shown) such that the signals from the quantizers 1140are time-multiplexed. The switch may be toggled at a constant rate, andmay be an example of the switch 316 discussed with respect to FIG. 3 .An illustrative graph 1130 shows that some time periods are occupied byconverted RHCP signals and other time periods are occupied by convertedLHCP signals in, e.g., a 1:1 ratio during transmission over the data bus1118.

The baseband subsystem 1120 may include a digital splitter 1144, whichreverses the combination performed by the digital combiner 1142. In someembodiments, the digital splitter 1144 may include another switch (notshown), which may be toggled synchronously at the same rate as theswitch associated with the digital combiner 1142.

The baseband subsystem 1120 may further include an RF coupler 1114 thatis configured to receive and combine inputs from the two antennas 1112.To this end, outputs from the digital splitter 1144 may be transmitteddirectly to the RF coupler 1114. In some embodiments, the RF coupler1114 may be a 90-degree hybrid coupler, configured to receive two inputsignals (e.g., vertically polarized and horizontally polarized) andoutput combined phase-shifted signals, e.g., RHCP and LHCP signals. RHCPand LHCP signals may be received at one or more receivers, such as RFreceiver modules 1122-1, 1122-2. Receiver modules 1122-1 and 1122-2 maybe examples of receivers 722-1 and 722-2 of FIG. 7 .

FIG. 12 illustrates a block diagram of a configuration of an antennasystem 1200 of a wireless device (e.g., a UE 105), according to anotherembodiment. The antenna system 1200 may include a plurality of receivingantennas, such as two antennas 1210 and 1220. Each of these antennas1210 and 1220 may be configured to detect linearly polarized signals orsignal components. In certain embodiments, each of the antennas 1210 and1220 may be a planar inverted-F antenna (PIFA) type antenna. Antennas1210 and 1220 may be examples of the antennas 312 discussed with respectto FIG. 3 .

In some embodiments, the antenna system 1200 may include at least oneextractor 1260, at least one tuner 1270, at least one diplexer 1280, anda 90-degree hybrid coupler 1214. In some embodiments, the tuner 1270 andthe diplexer 1280 may be substituted with another extractor and viceversa (i.e., the extractor 1260 may be substituted with another diplexerand/or another tuner). In other embodiments, the extractor 1260 and/orthe diplexer 1280 may be substituted with a triplexer or an N-plexerwith equal success. In certain embodiments, the diplexer 1280 mayinclude or be substituted with a switch. The switch may be configured totoggle transmission of different types of signals to differentcomponents of the UE, e.g., GNSS signals to the 90-degree hybrid coupler1214.

In some embodiments, the extractor 1260 may be configured to receive andremove multiple types wireless communication signals, e.g., WWAN andGNSS signals. For example, the extractor 1260 may extract the GNSSportion of the received signals and cause transmission of the GNSSsignals to the 90-degree hybrid coupler 1214. The extractor 1260 mayalso extract the WWAN portion of received signals and cause transmissionto another component or subsystem (not shown) of the UE which aresharing the antenna 1210.

Alternatively, using signals received at antenna 1220 as an example, thetuner 1270 may be configured to tune or optimize the reception of thereceived signal to one used for or suitable for GNSS positioningsignals. The diplexer 1280 may switch the signal transmission path tothe 90-degree hybrid coupler 1214, rather than to another component orsubsystem of the UE which are sharing the antenna 1220 (e.g., a WWANsubsystem, not shown).

In some embodiments, the 90-degree hybrid coupler 1214 is configured toreceive and combine inputs (e.g., vertically polarized and horizontallypolarized) from the two antennas 1210 and 1220 into an output signalhaving a different polarization type. For example, linearly polarizedcomponents obtained via the antennas 1210, 1220 may be combined tooutput into circularly polarized signals, e.g., RHCP or LHCP signals.The 90-degree hybrid coupler 1214 may also include a load resistor 1232(e.g., a 50-ohm load resistor) to terminate reflections from the inputcomponents (extractor 1260 and diplexer 1280) and maintain a highisolation between the input ports.

The antenna system 1200 may also include a diplexer 1250 configured toseparate two frequency bands of the incoming GNSS signals (such as L1and L5). Each type of signal may be received and processed (e.g.,demodulated) by respective receivers 1240. In some embodiments, thereceivers 1240 may include distinct receiver modules, which may beexamples of receivers 322-1 and 322-2 discussed with respect to FIG. 3 .

Other embodiments and configurations of the components discussed abovewill become apparent to one having ordinary skill in the relevant art,and the concepts described herein are not strictly limited to theforegoing embodiments of FIGS. 3-12 . Some components may be optionaland additional components may be added for achieving similar results.Portions of one embodiment may be combined with portions of anotherembodiment.

Polarization Profiles

FIG. 13 is a table 1300 showing illustrative examples of determinationsthat may be made regarding multipath and classifications ofenvironmental contexts based on right-handed and left-handed componentsof positioning signals. The table 1300 compares (i) environmentalcontexts or conditions, (ii) signal strength or attenuation of theright-handed circular polarization (RHCP) component of a receivedpositioning signal, (iii) signal strength or attenuation of theleft-handed circular polarization (LHCP) component of the receivedpositioning signal, (iv) signal strength or attenuation of linear (LV orLH) components of the received signal, and/or (v) likely determinationsthat may be made based on these polarization profiles or behaviors. Inthese examples, C/No may be used to measure relative signal strengths ofthe positioning signals.

In some embodiments, to obtain these relative signal strengths,measurements of RHCP and LHCP components (and linear polarization ifavailable) may be performed closely in time (ideally nearsimultaneously) and not separated by a significant temporal gap. This isto ensure that the signal environment is largely similar when themeasurements are performed, and to get an accurate relative differencein signal strengths for the multipath indication. Depending on the usescenario, however, the measurements may be performed with differentamounts of temporal gap. For example, if the UE is stationary, or ifprocessing resources have been reduced or diverted elsewhere, the amountof time between polarization measurements may be more forgiving(larger). However, if the UE is moving (e.g., the user is walking orinside a vehicle), the UE may perform the measurements as closely aspossible.

In example 1310, a received positioning signal is measured by the UE tohave relative signal strengths of 0 dB for the RHCP component and −30 dBfor the LHCP component (i.e., an attenuation of 30 dB relative to theRHCP component). RHCP and LHCP measurements may be obtained using any ofthe embodiments of FIGS. 3-12 . Specifically, in some embodiments, thesignal strengths measured in C/N₀ values may be determined by, e.g., oneor more receivers, such as receivers 322. An indication of 0 dB may notnecessarily correspond to a measurement of 0 dB but rather a referencelevel.

In some embodiments, relative values of signal strengths between RHCPand LHCP components are evaluated to make the multipath determination.For example, if the RHCP component of a signal had a greater signalstrength than the LHCP component by a difference of 30 dB or more (e.g.,0 dB vs. −30 dB), or of another amount that indicates dominance of onecomponent over the other, then the UE may determine with fair certaintythat the signal was a line-of-sight (LOS) signal. Moreover, a differenceof 30 dB may be considered considerably large when comparing RHCP andLHCP components. Although not dispositive to determination of multipath,the strength of a linear component may be detected in the signal aswell, −3 dB in this case.

It is noted that the absolute value of the relative difference alone isa portion of a useful determination of presence of multipath. Whencomparing relative differences, the UE also determines which of the RHCPand LHCP components is larger. Since satellites conventionally emit RHCPpositioning signals, the strong RHCP component and weak LHCP componentindicate that the received signal most likely did not interact withsurfaces in the environment (buildings, roads, etc.). That is, thepositioning signal is likely in its original form.

Based on these RHCP and LHCP measurements of 0 and −30 dB, respectively,and the relatively large difference between the measurements, the UE maymake a determination with respect to multipath. In this case, it can bedetermined that the received positioning signal likely had a LOS path;i.e., the signal was directly received from the SV (e.g., GNSSsatellite) with no reflections and thus no multipath. Based on thedetermination, the positioning signals and/or the SV(s) emitting thesignals may then be used or otherwise weighted heavily in positiondetermination.

In some embodiments, elevation and azimuth angles for the emitting SV(s)may be taken into account in the determination of multipath. Forexample, data corresponding to elevation and azimuth angles may be usedas additional data to train the UE or portions of the positioning system(e.g., the location server 160) using the aforementioned machinelearning implementations. Determining algorithmic parameters and weightsbased on the angles of the SV(s) may enable further accuracy indetermining multipath and/or classifications of the environmentalcontext, e.g., on a per-SV basis.

In some implementations, other types of information may be used inconjunction to determine multipath. For example, rough locations may beobtained based on WLAN- (e.g., Wi-Fi) or cellular-based positioning,which may indicate that a UE is in a certain known area (e.g., downtowncity streets with high likelihood of multipath).

In some implementations, the confidence level of multipath determinationmay also be improved based on prior measurement(s) or a “crowdsourced”database. More specifically, known information on polarization profiles(i.e., signal strengths of RHCP and LHCP components of positioningsignals) versus the associated environmental context may indicate apattern pertaining to a given polarization profile, thereby increasingthe confidence of the inference of the environment if the samepolarization profile has been determined. For example, a determinationof an RHCP signal component of 0 to 5 dB and a relative LHCP signalcomponent of −16 to −20 dB may have been determined by priormeasurements and determinations by the UE or other UEs (e.g., inconjunction with the aforementioned other types of information in someimplementations) to indicate an urban canyon with an even number ofreflections. In that case, obtained measurements of −1 dB RHCP and −20dB LHCP may fairly indicate multipath in an urban canyon with an evennumber of reflections, and cause de-weighting of the signal and/or theemitting SV. In some embodiments, the UE may be configured to contributeinformation related to detected signal strengths, multipath, and/orlocation (e.g., absolute or relative geodetic coordinates) as part ofusing the crowdsourced data.

In some implementations, the difference threshold may be predeterminedor dynamically determined based on factors such as time of day, networkcongestion (e.g., other UEs in proximity or using the GNSS sending thesignals), type of device, type of antennas used by the UE, or othercharacteristics of the UE. In some embodiments, the relative differenceof the RHCP and LHCP measurements may be evaluated with respect tothresholds that are predetermined or dynamically determined based onthese factors.

Referring now to example 1312, a received positioning signal is measuredto have a relative RHCP component of 0 dB and some small relative LHCPcomponent, e.g., between −15 and −25 dB, though in variousimplementations, this “small” range may be any range below 0 dB. In thiscase, the UE may make a determination with respect to multipath whereina small amount of reflection (i.e., a low-angle reflection) occurredafter the positioning signal was emitted from the satellite and beforeit reached the UE. Since the RHCP component remained large (0 dB), therewas likely a LOS transmission with small multipath errors on thereceived signal. The signals and/or the SV(s) emitting the positioningsignals would likely be weighted significantly in positiondetermination.

In example 1314, a received positioning signal is measured to have arelative RHCP component of 0 dB and some large relative LHCP component,e.g., between −10 and 0 dB. A different range of values (−5 to 0 dB byway of example) may also be considered “large.” In this case, the UE maymake a determination with respect to multipath wherein relatively largereflections occurred after the positioning signal was emitted from thesatellite and before it reached the UE. Since the LHCP component islarge (near 0 dB relative to the RHCP component), there was likely a LOStransmission with large multipath errors on the received signal. Here,the UE may determine that multipath (likely to result in large errors)occurred, and thus de-weight or disregard the transmitting SV(s) and/orthe positioning signal in the UE's location determination.

In example 1316, a received positioning signal is measured to have arelative RHCP component of −30 dB and 0 dB for the relative LHCPcomponent. As noted elsewhere herein, reflection of a circularlypolarized signal causes the polarization to change between right-handedand left-handed. Since GNSS satellites conventionally emit RHCP signals,receiving a signal having a weak RHCP component and a strong LHCPcomponent is indicative of a reflection, e.g., an isolated tall buildingproviding a surface from which the signal has reflected before arrivingat the UE. In this case, the UE may reject or disregard the signal basedon multipath. However, in some embodiments, although the presence ofmultipath has been detected, the UE may alternatively de-weight theSV(s) and/or the received signal to an extent, rather than entirelydisregarding, since a single reflection is not likely to causesignificant errors on the signal. Compare with example 1310, whererelative RHCP was 0 dB and relative LHCP was −30 dB.

In example 1318, a received positioning signal is measured to have asmall relative RHCP component and 0 dB for the relative LHCP component.Similar to example 1316, the large LHCP component indicates multipathreflections. More generally, signals that have reflected an odd numberof times (1, 3, 5, etc.) may keep a larger LHCP component since thehandedness of the signal will change upon each reflection. The UE maythen infer the presence of multipath in an “urban canyon” environmentwith many surfaces (e.g., surrounded by tall buildings, inside abuilding in a busy commercial area, within a tunnel). The UE mayde-weight or reject the SV(s) and/or the signal accordingly upondetermining this polarization profile.

In example 1320, a received positioning signal is measured to have arelative RHCP component of 0 dB and a small relative LHCP component. Asmall absolute RHCP component may indicate that multipath anddegradation of the signal may have occurred over an even number of times(2, 4, 6, etc.), causing further degradation of the signal (e.g.,C/N₀<−30 dB) or additive effects (e.g., C/N₀<−20 and C/N₀>−30 dB).Similar to example 1318, the UE may determine the presence of multipathin an “urban canyon” environment with many surfaces. The UE mayde-weight or reject the SV(s) and/or the signal accordingly.

Finally, in example 1322, a mixture of small to large relative signalstrength measurements for the RHCP and LHCP components may bedetermined. This may indicate a high likelihood that multipath hasoccurred with a significant amount of degradation of the initialpositioning signal. This type of positioning signal may not be valuableto location determination, and thus, the UE may reject the SV(s) and/orthe signal. In some embodiments, the SV(s) and/or the signal may bede-weighted instead.

Thus, relative signal strengths of RHCP, LHCP, as well as linearpolarization results if available, may be used for multipathdetermination or assessment. Myriad other scenarios, combinations ofpolarizations, and conclusions will become apparent to those havingordinary skill in the art, the above examples being purely illustrative.

Data on these relationships between RHCP and LHCP polarizations of thereceived positioning signals and the likely determinations of multipathand the type of environment may be stored or accessible by the UE (e.g.,wirelessly at a server, an access point, or a remote database), enablingone or more of the UE components (as shown in FIG. 13 ) to weight,de-weight, or reject certain SV(s) and/or positioning signals whileperforming location determination or location estimation. Generally,positioning signals that have experienced degradation (caused by, e.g.,multipath) are more prone to error and thus less relevant forpositioning, since data encompassed by positioning signals as discussedabove, for example, may lose integrity after signal degradation.Therefore, positioning signals that have not experienced multipath aremore useful and can provide additional support for an accurate andefficient position determination process.

However, positioning signals of any degree of RHCP and LHCP polarizationthat have been received by the UE may be highly relevant and useful forthe location determination process. In the above examples, multipathdetection was possible because of relationships between polarizationcharacteristics and environmental context were previously determined bythe UE 105 or another UE or device, and/or accessible locally on the UEor at another network device (e.g., an access point or a server). Thus,storing, or even “crowdsourcing” of polarization profiles by one or moreUEs of the network, for example by having accessible data onpolarization profiles via the network 170, may allow a given UE toquickly and efficiently determine the characteristics of its locationand/or determine or estimate its location based at least on previouslydetermined relationships between (i) signal strengths of the RHCP andLHCP polarization components of received positioning signals and (ii)location (e.g., a particular intersection of a downtown city area).Additionally, in some embodiments, if the GNSS pseudorange (e.g.,determined based on the travel time of a positioning signal from the SVto the UE) associated with a first signal having one predominantpolarization type (e.g., RHCP component) is determined to be longer thanthe pseudorange associated with another signal having anotherpredominant polarization type (e.g., LHCP component), then it mayindicate that the first signal did not take a direct path, and mayindicate a multipath-degraded signal based thereon. Therefore, the UEmay not only determine an indication of multipath based on signalstrengths, but the UE may contribute information related to detectedsignal strengths, pseudoranges, and location (e.g., absolute or relativegeodetic coordinates). Such information may be transmitted to, e.g., thelocation server 160, or stored more locally at an access point.

Example Techniques

FIG. 14 is a flow diagram of a method 1400 of determining the presenceof multipath during positioning of a mobile device, according to oneembodiment. One or more of the functions of the method 1400 may beperformed by a wireless device (e.g., UE 105) that is capable ofreceiving positioning signals an SV (e.g., GNSS satellite). Means forperforming the functionality illustrated in one or more of the blocksshown in FIG. 14 may include hardware and/or software components of a UEsuch as the UE 105 shown in FIGS. 1 and 2 . Example components of a UEare illustrated in FIG. 16 , which are described in more detailelsewhere herein.

At step 1410 of the method 1400, the functionality includes determininga first indication of a signal strength associated with a firstpolarization type and derived from one or more signals received from atleast one SV (e.g., a GNSS satellite) using one or more antennas at themobile device. The signal strength may be measured from one or morepositioning signals received from a GNSS satellite using the antennas ofa mobile device (e.g., UE 105). The UE may utilize linearly polarizedantennas such as those discussed above (e.g., antennas 312) to detectpositioning signals from the GNSS satellite. For example, a verticallypolarized component of a signal may be detected by one antenna on theUE, and a horizontally polarized component of the signal may be detectedby another antenna on the UE. The vertical and horizontal components maybe inputted into an RF coupler (e.g., a 90-degree hybrid coupler) togenerate a circularly polarized signal. The outputted circularlypolarized signal may be transmitted to a baseband subsystem formeasurement of signal strength of the first polarization type, e.g., theright-handed polarization component. The signal strength may bedetermined and measured by a receiver (e.g., receiver 322) in terms ofC/N₀ (dB).

In another embodiment, at least one of the antennas may be configured todetect circularly polarized signals directly. At least one of theantennas may be an RHCP antenna or an LHCP antenna respectivelyconfigured to detect and receive RHCP signals or LHCP signals. Thesignal strength of the first polarization type (e.g., right-handed) ofthe circularly polarized signal may be transmitted to and determined bythe baseband subsystem.

Given that positioning signals are emitted as RHCP signals, multipathcaused by reflection from various surfaces in the local environment onthe surface of the globe may cause the received signals to be at leastpartly right-handed and at least partly left-handed as previouslydiscussed.

To that end, at step 1420 of the method 1400, the functionality includesdetermining a second indication of a signal strength associated with asecond polarization type and derived from the one or more signalsreceived from the GNSS satellite using the one or more antennas at themobile device. Similar to step 1410, the UE may measure the signalstrength (e.g., C/N₀) of the second polarization type, e.g., theleft-handed component of signals received by the one or more antennas.In some cases, the signal strength of the LHCP component may besignificant, while in some cases, the signal strength may be negligible.The LHCP signal strength may vary from small to large, as shown in theexamples of FIG. 13 .

At step 1430, the functionality includes, based on the first indicationof signal strength associated with the first polarization type (fromstep 1410), and the second indication of signal strength associated withthe second polarization type (from step 1420), determining an indicationof multipath reflection along a path of signal propagation between theGNSS satellite and the mobile device. In one embodiment, the firstindication of signal strength associated with the first polarizationtype may include a first C/N₀ value for the right-handed component of areceived signal, and the second indication of signal strength associatedwith the second polarization type may include a second C/N₀ value forthe left-handed component of a received signal. The indication ofmultipath may be determined based on the first and second C/N₀ values.More specifically, in some embodiments, the relative signal strengths ofthe RHCP and LHCP polarization types enable determination of multipathand an inference of environmental context, as discussed with respect toFIG. 13 .

In one example scenario, the measurement by the UE 105 may indicate,based on the first and second indications of signal strength of thereceived signal, that a received positioning signal has a largeright-handed component (e.g., relative 0 dB) and a small left-handedcomponent (e.g., −30 dB), which may indicate that the positioning signalwas likely received in a line of sight from the SV with minimal to noreflections (i.e., no multipath), and that the positioning signal and/orthe SV emitting this positioning signal should be weighted heavily forposition determination.

In another example scenario, the received positioning signal may have asmall right-handed component and a large left-handed component. Thepresence of a strong left-handed polarization indicates multipath in thepositioning signal. This type of positioning signal might be used inlocation determination by a prior positioning system that is not usingthe methodology described herein. However, the present disclosure mayconsider this signal to be under the influence of multipath and thus notrelevant to accurately determining its position. That is, even thoughthe left-handed component of the signal is strong, the methodologydescribed in the present disclosure does not necessarily find itvaluable for position determination because the presence of a strongleft-handed component is an indication that the positioning signal mayhave degraded due to multipath. The UE may thus de-weight thetransmitting SV(s) and/or the positioning signal, or completelydisregard this type of positioning signal in its location solution.

In many embodiments, means for performing functionality at steps 1410,1420 and 1430 may comprise a signal path or a bus 1605, processor(s)1610, digital signal processor (DSP) 1620, GNSS receiver 1680, one ormore antennas 1682, and/or other components of a UE, as illustrated inFIG. 16 . In some embodiments, means for performing functionality atsteps 1410, 1420 and 1430 may comprise a signal path or a bus 1705,processor(s) 1710, DSP 1720, and wireless communication antenna(s) 1732,and/or other components of Transmission Reception Point (TRP), asillustrated in FIG. 17 . A TRP may be part of an access point such asbase station 120 or AP 130 that detects signals on behalf of the UE 105and provides location estimation data for the UE 105.

FIG. 15 is a flow diagram of a method 1500 of determining the presenceof multipath during positioning of a mobile device, according to anotherembodiment. One or more of the functions of the method 1500 may beperformed by a wireless device (e.g., UE 105) that is capable ofreceiving positioning signals an SV (e.g., GNSS satellite). Means forperforming the functionality illustrated in one or more of the blocksshown in FIG. 15 may include hardware and/or software components of a UEsuch as the UE 105 shown in FIGS. 1 and 2 . Example components of a UEare illustrated in FIG. 16 , which are described in more detailelsewhere herein.

At step 1510, the method may include receiving one or more positioningsignals. In some embodiments, the positioning signals are emitted fromat least one SV (e.g., GNSS satellite). The positioning signals may bedetected by one or more antennas of the UE.

At step 1520, the method may include obtaining metrics associated withthe received positioning signals. In some embodiments, the metrics mayinclude indications relating to polarization types, which may includecircular polarization components of the received positioning signals,i.e., RHCP and LHCP components. The metrics to measure the circularpolarization components may include signal strengths represented by C/N₀values measured in dB. In some embodiments, the C/N₀ values may bedetermined by receivers (e.g., 322) of a baseband subsystem. Inalternate embodiments, the metrics may include data indicative of thepseudorange associated with a positioning signal.

At step 1530, the method may include determining presence of multipathon the positioning signals based on the obtained metrics. In someembodiments, the metrics (e.g., C/N₀ values) may be compared relative toeach other. For example, the relative C/N₀ values may be −30 dB on theRHCP component of the received positioning signals and 0 dB on the LHCPcomponent. This may result in a determination of multipath, and furtherresult in an inference that a single reflection occurred from a surface.Other comparisons between RHCP and LHCP components may reveal othertypes of environmental context (urban canyon, open-field line of sight,etc.), as discussed with respect to FIG. 13 . In some embodiments, thepseudorange associated with a signal having RHCP polarization may becompared to the pseudorange associated with a signal having LHCPpolarization, and any difference between the pseudoranges may indicatethe presence of multipath. For example, if the RHCP pseudorangeindicates a longer path than the LHCP (or linear) pseudorange, this maybe indicative of the RHCP signal being a multipath-degraded signal.

In some embodiments, the relationships between C/N₀ values andenvironmental context may already exist from prior “crowdsourced” datathat is accessible via a network (e.g., stored and maintained in a basestation 120 or the location server 160). Such data may contain knowninformation on polarization profiles (i.e., signal strengths of RHCP andLHCP components of positioning signals) and the associated environmentalcontext. Such crowdsourced data may assist with the determination of thepresence of multipath by improving a confidence level of thedetermination, as described with respect to FIG. 13 .

At step 1540, the method may include determining or estimating theposition of the mobile device based on the determination of the presenceof multipath. In some embodiments, determining or estimating theposition includes determining a utilization plan for the signals fromthe GNSS satellite, based on the indication of multipath reflectionbetween the GNSS satellite and the mobile device, or the extent to whichmultipath has affected the positioning signals. The received positioningsignals (or a position fix derived from the signals) and/or the SV(s)that have emitted the signals may be assigned a weight in the locationsolution, or the signals and/or the SV(s) may be de-weighted ordisregarded in the location solution.

It will be appreciated that some or all of the above steps of FIG. 15may be performed by a network entity other than the UE (e.g., TRP) forthe determination of multipath and location with respect to a given UE.

Additional Use Cases

In some implementations, the configurations and methods described hereinmay be used to determine the presence of a signal spoofing source.

Spoofing refers to obscuring of a location, such as a location of a UEor a moving vehicle (e.g., a ship). One type of spoofing may involvetransmission and/or delayed retransmission of GNSS signals from a singletransmitting antenna. A target receiver that detects such GNSS signalsmay appear to be in a location different from the actual location of thetarget receiver. A spoofing source may appear to be in a differentlocation to a monitoring system.

Spoofed signals retain their multipath characteristics (e.g.,polarization profiles). Hence, with the various antenna configurationsand determination methodologies described above where RHCP and LHCPsignals are measured, a receiver may be able to distinguish spoofedsignals from true signals. For true signals, the signals are beingtransmitted from different SVs at different elevation and azimuthangles, and hence will have different polarization characteristicsbetween each one. For spoofed signals, the spoofing source antenna maybe configured to emit RH, LH, or linear signals. However, thepolarization characteristics for all SVs will be nearly identical, forthe same carrier frequency (e.g., L1 or L5). For example, RHCP-to-LHCPsignal strength ratios and/or relative peak locations will be verysimilar because of the similar multipath signatures from the spoofingsource.

Therefore, by determining the polarization characteristics andassociated multipath signatures based on the measurements, andevaluating them for a similarity level, a receiver may determine whetherthe GNSS signals may be spoofed. For example, RHCP and LHCP componentsmay be measured for signals from each SV and compared to see if they arewithin an unacceptable range; e.g., variations of less than 1 dB amongreadings may indicate a possibility of spoofing. The amount of variationmay be determined based on specific usage scenarios.

In some scenarios, strong in-band jamming may affect certain frequencies(e.g., L1 or L5). For example, a re-transmitter device (i.e., a jammer)may be installed to boost GNSS signals inside a vehicle because a usermay experience signals that do not appear to be strong enough, e.g.,inside a vehicle or enclosure. The user may desire stronger GPS signalsbut not aware of the impact such excessively strong signals may have ona UE's circuitry. The re-transmitter device may receive and amplify onlyGPS L1 signals and re-radiate those signals into the vehicle. However,this very strong signal (amplified by, e.g., 40-50 dB) can saturate andthereby desensitize the L1 receiver on a UE.

To prevent the saturation of the L1 receiver saturation, thepolarization of the re-radiated signals may be detected. The re-radiatedsignals likely will not have the same polarization as the incoming L1signal (which is mainly RHCP). Hence, signal paths corresponding to thedetected polarization of the re-radiated signals may be downregulated orotherwise sampled less. As an example, if the re-radiated signals aredetermined to have an RHCP component of 10 dB and LHCP component of 30dB, a switch (e.g., 316) may toggle so as to sample more of the RHCPsignals than the LHCP signals, and/or, the receiver(s) at the UE mayreduce the contributions from the suspect signals to the overallposition solution. The polarization for the L1 antenna may be changedindependently of other receivers (such as L5) to attenuate there-radiated signals.

In some cases, if the UE determines that polarization characteristicsfrom re-radiated signals are similar, then the UE may determine that thesignals are coming from one source, i.e., the jammer. The UE may respondsimilarly, e.g., reduce contributions from the suspect signals and/orsample more RHCP signals.

This is an application of the techniques described herein which isopposite to determining the polarization. Farther than best receivingthe signal, in this scenario, a powerful signal can be reduced orattenuated according to the polarization.

Example System Configurations

FIG. 16 illustrates an embodiment of a UE 105, which can be utilized asdescribed herein above. For example, the UE 105 can perform one or moreof the functions of the method shown in FIGS. 14 and 15 . It should benoted that FIG. 16 is meant only to provide a generalized illustrationof various components, any or all of which may be utilized asappropriate. It can be noted that, in some instances, componentsillustrated by FIG. 16 can be localized to a single physical deviceand/or distributed among various networked devices, which may bedisposed at different physical locations. Furthermore, as previouslynoted, the functionality of the UE discussed in the previously describedembodiments may be executed by one or more of the hardware and/orsoftware components illustrated in FIG. 16 .

The UE 105 is shown comprising hardware elements that can beelectrically coupled via a bus 1605 (or may otherwise be incommunication, as appropriate). The hardware elements may include aprocessor(s) 1610 which can include without limitation one or moregeneral-purpose processors (e.g., an application processor), one or morespecial-purpose processors (such as digital signal processor (DSP)chips, graphics acceleration processors, application specific integratedcircuits (ASICs), and/or the like), and/or other processing structuresor means. Processor(s) 1610 may comprise one or more processing units,which may be housed in a single integrated circuit (IC) or multiple ICs.As shown in FIG. 16 , some embodiments may have a separate DSP 1620,depending on desired functionality. Location determination and/or otherdeterminations based on wireless communication may be provided in theprocessor(s) 1610 and/or wireless communication interface 1630(discussed below). The UE 105 also can include one or more input devices1670, which can include without limitation one or more keyboards, touchscreens, touch pads, microphones, buttons, dials, switches, and/or thelike; and one or more output devices 1615, which can include withoutlimitation one or more displays (e.g., touch screens), light emittingdiodes (LEDs), speakers, and/or the like.

The UE 105 may also include a wireless communication interface 1630,which may comprise without limitation a modem, a network card, aninfrared communication device, a wireless communication device, and/or achipset (such as a Bluetooth® device, an IEEE 802.11 device, an IEEE802.15.4 device, a Wi-Fi device, a WiMAX device, a WAN device, and/orvarious cellular devices, etc.), and/or the like, which may enable theUE 105 to communicate with other devices as described in the embodimentsabove. The wireless communication interface 1630 may permit data andsignaling to be communicated (e.g., transmitted and received) with TRPsof a network, for example, via eNBs, gNBs, ng-eNBs, access points,various base stations and/or other access node types, and/or othernetwork components, computer systems, and/or any other electronicdevices communicatively coupled with TRPs, as described herein. Thecommunication can be carried out via one or more wireless communicationantenna(s) 1632 that send and/or receive wireless signals 1634.According to some embodiments, the wireless communication antenna(s)1632 may comprise a plurality of discrete antennas, antenna arrays, orany combination thereof. The antenna(s) 1632 may be capable oftransmitting and receiving wireless signals using beams (e.g., Tx beamsand Rx beams). Beam formation may be performed using digital and/oranalog beam formation techniques, with respective digital and/or analogcircuitry. The wireless communication interface 1630 may include suchcircuitry.

Depending on desired functionality, the wireless communication interface1630 may comprise a separate receiver and transmitter, or anycombination of transceivers, transmitters, and/or receivers tocommunicate with base stations (e.g., ng-eNBs and gNBs) and otherterrestrial transceivers, such as wireless devices and access points.The UE 105 may communicate with different data networks that maycomprise various network types. For example, a Wireless Wide AreaNetwork (WWAN) may be a CDMA network, a Time Division Multiple Access(TDMA) network, a Frequency Division Multiple Access (FDMA) network, anOrthogonal Frequency Division Multiple Access (OFDMA) network, aSingle-Carrier Frequency Division Multiple Access (SC-FDMA) network, aWiMAX (IEEE 802.16) network, and so on. A CDMA network may implement oneor more RATs such as CDMA2000®, WCDMA, and so on. CDMA2000® includesIS-95, IS-2000 and/or IS-856 standards. A TDMA network may implementGSM, Digital Advanced Mobile Phone System (D-AMPS), or some other RAT.An OFDMA network may employ LTE, LTE Advanced, 5G NR, and so on. 5G NR,LTE, LTE Advanced, GSM, and WCDMA are described in documents from 3GPP.CDMA2000® is described in documents from a consortium named “3rdGeneration Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents arepublicly available. A wireless local area network (WLAN) may also be anIEEE 802.11x network, and a wireless personal area network (WPAN) may bea Bluetooth network, an IEEE 802.15x, or some other type of network. Thetechniques described herein may also be used for any combination ofWWAN, WLAN and/or WPAN.

The UE 105 can further include sensor(s) 1640. Sensor(s) 1640 maycomprise, without limitation, one or more inertial sensors and/or othersensors (e.g., accelerometer(s), gyroscope(s), camera(s),magnetometer(s), altimeter(s), microphone(s), proximity sensor(s), lightsensor(s), barometer(s), and the like), some of which may be used toobtain position-related measurements and/or other information.

Embodiments of the UE 105 may also include a Global Navigation SatelliteSystem (GNSS) receiver 1680 capable of receiving signals 1684 from oneor more GNSS satellites using an antenna 1682 (which could be the sameas antenna 1632 or the antenna 312). Positioning based on GNSS signalmeasurement can be utilized to complement and/or incorporate thetechniques described herein. The GNSS receiver 1680 can extract aposition of the UE 105, using conventional techniques, from GNSSsatellites 110 of a GNSS system, such as Global Positioning System(GPS), Galileo, GLONASS, Quasi-Zenith Satellite System (QZSS) overJapan, IRNSS over India, BeiDou Navigation Satellite System (BDS) overChina, and/or the like. Moreover, the GNSS receiver 1680 can be usedwith various augmentation systems (e.g., a Satellite Based AugmentationSystem (SBAS)) that may be associated with or otherwise enabled for usewith one or more global and/or regional navigation satellite systems,such as, e.g., Wide Area Augmentation System (WAAS), EuropeanGeostationary Navigation Overlay Service (EGNOS), Multi-functionalSatellite Augmentation System (MSAS), and Geo Augmented Navigationsystem (GAGAN), and/or the like.

It can be noted that, although GNSS receiver 1680 is illustrated in FIG.16 as a distinct component, embodiments are not so limited. As usedherein, the term “GNSS receiver” may comprise hardware and/or softwarecomponents configured to obtain GNSS measurements (measurements fromGNSS satellites). In some embodiments, therefore, the GNSS receiver maycomprise a measurement engine executed (as software) by one or moreprocessors, such as processor(s) 1610, DSP 1620, and/or a processorwithin the wireless communication interface 1630 (e.g., in a modem). AGNSS receiver may optionally also include a positioning engine, whichcan use GNSS measurements from the measurement engine to determine aposition of the GNSS receiver using an Extended Kalman Filter (EKF),Weighted Least Squares (WLS), a hatch filter, particle filter, or thelike. The positioning engine may also be executed by one or moreprocessors, such as processor(s) 1610 or DSP 1620.

The UE 105 may further include and/or be in communication with a memory1660. The memory 1660 can include, without limitation, local and/ornetwork accessible storage, a disk drive, a drive array, an opticalstorage device, a solid-state storage device, such as a random accessmemory (RAM), and/or a read-only memory (ROM), which can beprogrammable, flash-updateable, and/or the like. Such storage devicesmay be configured to implement any appropriate data stores, includingwithout limitation, various file systems, database structures, and/orthe like.

The memory 1660 of the UE 105 also can comprise software elements (notshown in FIG. 16 ), including an operating system, device drivers,executable libraries, and/or other code, such as one or more applicationprograms, which may comprise computer programs provided by variousembodiments, and/or may be designed to implement methods, and/orconfigure systems, provided by other embodiments, as described herein.Merely by way of example, one or more procedures described with respectto the method(s) discussed above may be implemented as code and/orinstructions in memory 1660 that are executable by the UE 105 (and/orprocessor(s) 1610 or DSP 1620 within UE 105). In some embodiments, then,such code and/or instructions can be used to configure and/or adapt ageneral-purpose computer (or other device) to perform one or moreoperations in accordance with the described methods.

FIG. 17 illustrates an embodiment of a base station 120, which can beutilized in conjunction with some embodiments as described above. Itshould be noted that FIG. 17 is meant only to provide a generalizedillustration of various components, any or all of which may be utilizedas appropriate. In some embodiments, the base station 120 may correspondto a gNB, an ng-eNB, and/or (more generally) a TRP.

While many of the embodiments describe multipath estimation by a UE, thesame techniques may be used by a base station for multipath estimation.For example, knowing the multipath environment at the base station maybe used with the abovementioned crowdsourcing (e.g., by storing dataaccessible to nearby UEs).

The base station 120 is shown comprising hardware elements that can beelectrically coupled via a bus 1705 (or may otherwise be incommunication, as appropriate). The hardware elements may include aprocessor(s) 1710 which can include without limitation one or moregeneral-purpose processors, one or more special-purpose processors (suchas DSP chips, graphics acceleration processors, ASICs, and/or the like),and/or other processing structure or means. As shown in FIG. 17 , someembodiments may have a separate DSP 1720, depending on desiredfunctionality. Location determination and/or other determinations basedon wireless communication may be provided in the processor(s) 1710and/or wireless communication interface 1730 (discussed below),according to some embodiments. The base station 120 also can include oneor more input devices, which can include without limitation a keyboard,display, mouse, microphone, button(s), dial(s), switch(es), and/or thelike; and one or more output devices, which can include withoutlimitation a display, light emitting diode (LED), speakers, and/or thelike.

The base station 120 might also include a wireless communicationinterface 1730, which may comprise without limitation a modem, a networkcard, an infrared communication device, a wireless communication device,and/or a chipset (such as a Bluetooth® device, an IEEE 802.11 device, anIEEE 802.15.4 device, a Wi-Fi device, a WiMAX device, cellularcommunication facilities, etc.), and/or the like, which may enable thebase station 120 to communicate as described herein. The wirelesscommunication interface 1730 may permit data and signaling to becommunicated (e.g., transmitted and received) to UEs, other basestations/TRPs (e.g., eNBs, gNBs, and ng-eNBs), and/or other networkcomponents, computer systems, and/or any other electronic devicesdescribed herein. The communication can be carried out via one or morewireless communication antenna(s) 1732 that send and/or receive wirelesssignals 1734. These wireless communication antenna(s) may include theantenna(s) 312.

The base station 120 may also include a network interface 1780, whichcan include support of wireline communication technologies. The networkinterface 1780 may include a modem, network card, chipset, and/or thelike. The network interface 1780 may include one or more input and/oroutput communication interfaces to permit data to be exchanged with anetwork, communication network servers, computer systems, and/or anyother electronic devices described herein.

In many embodiments, the base station 120 may further comprise a memory1760. The memory 1760 can include, without limitation, local and/ornetwork accessible storage, a disk drive, a drive array, an opticalstorage device, a solid-state storage device, such as a RAM, and/or aROM, which can be programmable, flash-updateable, and/or the like. Suchstorage devices may be configured to implement any appropriate datastores, including without limitation, various file systems, databasestructures, and/or the like.

The memory 1760 of the base station 120 also may comprise softwareelements (not shown in FIG. 17 ), including an operating system, devicedrivers, executable libraries, and/or other code, such as one or moreapplication programs, which may comprise computer programs provided byvarious embodiments, and/or may be designed to implement methods, and/orconfigure systems, provided by other embodiments, as described herein.Merely by way of example, one or more procedures described with respectto the method(s) discussed above may be implemented as code and/orinstructions in memory 1760 that are executable by the base station 120(and/or processor(s) 1710 or DSP 1720 within base station 120). In someembodiments, then, such code and/or instructions can be used toconfigure and/or adapt a general-purpose computer (or other device) toperform one or more operations in accordance with the described methods.

It will be apparent to those skilled in the art that substantialvariations may be made in accordance with specific requirements. Forexample, customized hardware might also be used and/or particularelements might be implemented in hardware, software (including portablesoftware, such as applets, etc.), or both. Further, connection to othercomputing devices such as network input/output devices may be employed.

With reference to the appended figures, components that can includememory can include non-transitory machine-readable media. The term“machine-readable medium” and “computer-readable medium” as used herein,refer to any storage medium that participates in providing data thatcauses a machine to operate in a specific fashion. In embodimentsprovided hereinabove, various machine-readable media might be involvedin providing instructions/code to processors and/or other device(s) forexecution. Additionally or alternatively, the machine-readable mediamight be used to store and/or carry such instructions/code. In manyimplementations, a computer-readable medium is a physical and/ortangible storage medium. Such a medium may take many forms, includingbut not limited to, non-volatile media and volatile media. Common formsof computer-readable media include, for example, magnetic and/or opticalmedia, any other physical medium with patterns of holes, a RAM, aprogrammable ROM (PROM), erasable PROM (EPROM), a FLASH-EPROM, any othermemory chip or cartridge, or any other medium from which a computer canread instructions and/or code.

The methods, systems, and devices discussed herein are examples. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, features described with respectto certain embodiments may be combined in various other embodiments.Different aspects and elements of the embodiments may be combined in asimilar manner. The various components of the figures provided hereincan be embodied in hardware and/or software. Also, technology evolvesand, thus many of the elements are examples that do not limit the scopeof the disclosure to those specific examples.

It has proven convenient at times, principally for reasons of commonusage, to refer to such signals as bits, information, values, elements,symbols, characters, variables, terms, numbers, numerals, or the like.It should be understood, however, that all of these or similar terms areto be associated with appropriate physical quantities and are merelyconvenient labels. Unless specifically stated otherwise, as is apparentfrom the discussion above, it is appreciated that throughout thisSpecification discussion utilizing terms such as “processing,”“computing,” “calculating,” “determining,” “ascertaining,”“identifying,” “associating,” “measuring,” “performing,” or the likerefer to actions or processes of a specific apparatus, such as a specialpurpose computer or a similar special purpose electronic computingdevice. In the context of this Specification, therefore, a specialpurpose computer or a similar special purpose electronic computingdevice is capable of manipulating or transforming signals, typicallyrepresented as physical electronic, electrical, or magnetic quantitieswithin memories, registers, or other information storage devices,transmission devices, or display devices of the special purpose computeror similar special purpose electronic computing device.

Terms, “and” and “or” as used herein, may include a variety of meaningsthat also is expected to depend, at least in part, upon the context inwhich such terms are used. Typically, “or” if used to associate a list,such as A, B, or C, is intended to mean A, B, and C, here used in theinclusive sense, as well as A, B, or C, here used in the exclusivesense. In addition, the term “one or more” as used herein may be used todescribe any feature, structure, or characteristic in the singular ormay be used to describe some combination of features, structures, orcharacteristics. However, it should be noted that this is merely anillustrative example and claimed subject matter is not limited to thisexample. Furthermore, the term “at least one of” if used to associate alist, such as A, B, or C, can be interpreted to mean any combination ofA, B, and/or C, such as A, AB, AA, AAB, AABBCCC, etc.

Having described several embodiments, various modifications, alternativeconstructions, and equivalents may be used without departing from thescope of the disclosure. For example, the above elements may merely be acomponent of a larger system, wherein other rules may take precedenceover or otherwise modify the application of the various embodiments.Also, a number of steps may be undertaken before, during, or after theabove elements are considered. Accordingly, the above description doesnot limit the scope of the disclosure.

In view of this description embodiments may include differentcombinations of features. Implementation examples are described in thefollowing numbered clauses:

Clause 1: A method for multipath estimation at a mobile device,comprising: determining a first indication of signal strength associatedwith a first polarization type and derived from one or more signalsreceived from a GNSS satellite using one or more antennas at the mobiledevice; determining a second indication of signal strength associatedwith a second polarization type and derived from the one or more signalsreceived from the GNSS satellite using the one or more antennas at themobile device; and based on the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type,determining an indication of multipath reflection along a path of signalpropagation between the GNSS satellite and the mobile device.

Clause 2: The method of clause 1, further comprising: determining autilization plan for signals associated with the GNSS satellite, basedon the indication of multipath reflection between the GNSS satellite andthe mobile device.

Clause 3: The method of any of clauses 1-2 wherein the utilization plancomprises assigning a weight to signals or a position fix derived fromsignals from the GNSS satellite in estimating a position for the mobiledevice.

Clause 4: The method of any of clauses 1-3 wherein the utilization plancomprises utilizing signals from the GNSS satellite for estimating aposition for the mobile device.

Clause 5: The method of any of clauses 1-4 wherein the utilization plancomprises utilizing signals based on communication protocols other thanthe GNSS satellite for estimating a position for the mobile device.

Clause 6: The method of any of clauses 1-5 wherein the utilization planis further applied to signals from one or more other GNSS satellitesfrom one or more GNSS constellations.

Clause 7: The method of any of clauses 1-6 further comprising receivinga right-handed circularly polarized (RHCP) signal and a left-handedcircularly polarized (LHCP) signal, as time-multiplexed signals, over asingle signal path from an antenna subsystem; generating the firstindication of signal strength associated with the first polarizationtype from the RHCP signal; and generating the second indication ofsignal strength associated with the second polarization type from theLHCP signal.

Clause 8: The method of any of clauses 1-7 further comprising receivinga right-handed circularly polarized (RHCP) signal over a first signalpath from an antenna subsystem; receiving a left-handed circularlypolarized (LHCP) signal over a second signal path from the antennasubsystem; generating the first indication of signal strength associatedwith the first polarization type from the RHCP signal; and generatingthe second indication of signal strength associated with the secondpolarization type from the LHCP signal.

Clause 9: The method of any of clauses 1-8 further comprising receivinga first linearly polarized signal over a first signal path from anantenna subsystem; receiving second linearly polarized signal over asecond signal path from the antenna subsystem; converting the firstlinearly polarized signal and the second linearly polarized signal to aright-handed circularly polarized (RHCP) signal and a left-handedcircularly polarized (LHCP) signal; generating the first indication ofsignal strength associated with the first polarization type from theRHCP signal; and generating the second indication of signal strengthassociated with the second polarization type from the LHCP signal.

Clause 10: The method of any of clauses 1-9 further comprising receivinga right-handed circularly polarized (RHCP) signal and a left-handedcircularly polarized (LHCP) signal, as frequency-multiplexed signals,over a single signal path from an antenna subsystem; generating thefirst indication of signal strength associated with the firstpolarization type from the RHCP signal; and generating the secondindication of signal strength associated with the second polarizationtype from the LHCP signal.

Clause 11: The method of any of clauses 1-10 further comprisingcontrolling one or more switches to select, at a first time, the one ormore signals received from the GNSS satellite and select, at a secondtime, one or more wide-area-network (WAN) signals received at the mobiledevice using the one or more antennas.

Clause 12: The method of any of clauses 1-11 further comprisingreceiving a right-handed circularly polarized (RHCP) signal and aleft-handed circularly polarized (LHCP) signal as digital data;generating the first indication of signal strength associated with thefirst polarization type from the RHCP signal; and generating the secondindication of signal strength associated with the second polarizationtype from the LHCP signal.

Clause 13: The method of any of clauses 1-12 wherein the determining ofthe indication of multipath reflection is further based on a relativecomparison between the first indication of signal strength associatedwith the first polarization type and the second indication of signalstrength associated with the second polarization type.

Clause 14: The method of any of clauses 1-13 wherein the determining ofthe indication of multipath reflection is further based on priormeasurement data relating to the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type, the priormeasurement data having been obtained by other mobile devices and beingaccessible to the mobile device.

Clause 15: The method of any of clauses 1-14 further comprisingdetermining a polarization profile based on the first indication ofsignal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, the polarization profile comprising a relationshipamong the first indication of signal strength, the second indication ofsignal strength, a multipath characteristic associated with the one ormore signals received from the GNSS satellite, and an environmentalcontext.

Clause 16: The method of any of clauses 1-15 further comprisingdetermining, based at least on the polarization profile and theindication of multipath reflection, a presence of a signal spoofingsource associated with the one or more signals received from the GNSSsatellite.

Clause 17: The method of any of clauses 1-16 further comprisingdetermining, based on the first indication of signal strength associatedwith the first polarization type and the second indication of signalstrength associated with the second polarization type, an amplificationof the one or more signals received from the GNSS satellite; andresponsive to the determining of the amplification of the one or moresignals, mitigating the amplification by adjusting receipt of at leastone of the first polarization type or the second polarization type.

Clause 18: A user equipment comprising: a baseband subsystem; an antennasubsystem configured for signal communication with a baseband subsystem,the antenna subsystem comprising a first antenna, a second antenna, anda radio frequency (RF) coupler configured to receive signal inputs fromthe first antenna and the second antenna to output a signal having afirst polarization type and a signal having a second polarization type;and a processor, communicatively connected to the baseband subsystem,the processor configured to: determine a first indication of signalstrength associated with the first polarization type and derived fromone or more signals received from a GNSS satellite using the antennasubsystem; determine a second indication of signal strength associatedwith the second polarization type and derived from the one or moresignals received from the GNSS satellite using the antenna subsystem;and based on the first indication of signal strength associated with thefirst polarization type and the second indication of signal strengthassociated with the second polarization type, determine an indication ofmultipath reflection along a path of signal propagation between the GNSSsatellite and the user equipment.

Clause 19: The user equipment of clause 18, wherein the basebandsubsystem comprises a first receiver and a second receiver, the firstreceiver configured to determine the first indication of signal strengthassociated with the first polarization type, the second receiverconfigured to determine the second indication of signal strengthassociated with the second polarization type.

Clause 20: The user equipment of any of clauses 18-19 wherein the firstantenna is configured to detect a signal component having a verticalpolarization; the second antenna is configured to detect a signalcomponent having a horizontal polarization; and the RF coupler isfurther configured to combine the signal component having the verticalpolarization and the signal component having the horizontal polarizationto output a circularly polarized signal, the circularly polarized signalcomprising a right-handed circularly polarized (RHCP) signal componentand a left-handed circularly polarized (LHCP) signal component.

Clause 21: The user equipment of any of clauses 18-20 wherein theprocessor is further configured to: receive a right-handed circularlypolarized (RHCP) signal and a left-handed circularly polarized (LHCP)signal, as time-multiplexed signals, over a single signal path from theantenna subsystem; generate the first indication of signal strengthassociated with the first polarization type from the RHCP signal; andgenerate the second indication of signal strength associated with thesecond polarization type from the LHCP signal.

Clause 22: The user equipment of any of clauses 18-21 wherein theprocessor is further configured to: receive a right-handed circularlypolarized (RHCP) signal and a left-handed circularly polarized (LHCP)signal, as frequency-multiplexed signals, over a single signal path fromthe antenna subsystem; generate the first indication of signal strengthassociated with the first polarization type from the RHCP signal; andgenerate the second indication of signal strength associated with thesecond polarization type from the LHCP signal.

Clause 23: The user equipment of any of clauses 18-22 wherein thedetermination of the indication of multipath reflection is further basedon a relative comparison between the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type.

Clause 24: A non-transitory computer-readable apparatus comprising astorage medium, the storage medium comprising a plurality ofinstructions to, when executed by a processor, cause a mobile device to:determine a first indication of signal strength associated with a firstpolarization type and derived from one or more signals received from aGNSS satellite using one or more antennas at the mobile device;determine a second indication of signal strength associated with asecond polarization type and derived from the one or more signalsreceived from the GNSS satellite using the one or more antennas at themobile device; and based on the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type, determinean indication of multipath reflection along a path of signal propagationbetween the GNSS satellite and the mobile device.

Clause 25: The non-transitory computer-readable apparatus of clause 24,further comprising instructions to, when executed by the processor,cause the mobile device to: receive a right-handed circularly polarized(RHCP) signal and a left-handed circularly polarized (LHCP) signal, astime-multiplexed signals, over a single signal path from an antennasubsystem; generate the first indication of signal strength associatedwith the first polarization type from the RHCP signal; and generate thesecond indication of signal strength associated with the secondpolarization type from the LHCP signal.

Clause 26: The non-transitory computer-readable apparatus of any ofclauses 24-25, further comprising instructions to, when executed by theprocessor, cause the mobile device to: receive a right-handed circularlypolarized (RHCP) signal and a left-handed circularly polarized (LHCP)signal, as frequency-multiplexed signals, over a single signal path froman antenna subsystem; generate the first indication of signal strengthassociated with the first polarization type from the RHCP signal; andgenerate the second indication of signal strength associated with thesecond polarization type from the LHCP signal.

Clause 27: The non-transitory computer-readable apparatus of any ofclauses 24-26 wherein the determination of the indication of multipathreflection is further based on a relative comparison between the firstindication of signal strength associated with the first polarizationtype and the second indication of signal strength associated with thesecond polarization type.

Clause 28: A computerized apparatus comprising: means for determining afirst indication of signal strength associated with a first polarizationtype and derived from one or more signals received from a GNSS satelliteusing one or more antennas; means for determining a second indication ofsignal strength associated with a second polarization type and derivedfrom the one or more signals received from the GNSS satellite using theone or more antennas; and means for, based on the first indication ofsignal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determining an indication of multipath reflectionalong a path of signal propagation from the GNSS satellite.

Clause 29: The computerized apparatus of clause 28, wherein the meansfor determining the first indication of signal strength associated withthe first polarization type comprise a dedicated right-handed circularlypolarized (RHCP) antenna, and the means for receiving the secondindication of signal strength associated with the second polarizationtype comprise a dedicated left-handed circularly polarized (LHCP)antenna.

Clause 30: The computerized apparatus of any of clauses 28-29 furthercomprising means for receiving the one or more signals from the GNSSsatellite, the means for receiving the one or more signals from the GNSSsatellite comprising a first antenna configured to detect a signalcomponent having a vertical polarization, and a second antennaconfigured to detect a signal component having a horizontalpolarization; and means for combining the signal component having thevertical polarization and the signal component having the horizontalpolarization to output a circularly polarized signal, the circularlypolarized signal comprising a right-handed circularly polarized (RHCP)signal component and a left-handed circularly polarized (LHCP) signalcomponent.

What is claimed is:
 1. A method for multipath estimation at a mobiledevice, comprising: determining a first indication of signal strengthassociated with a first polarization type and derived from one or moresignals received from a GNSS satellite using one or more antennas at themobile device; determining a second indication of signal strengthassociated with a second polarization type and derived from the one ormore signals received from the GNSS satellite using the one or moreantennas at the mobile device; and based on the first indication ofsignal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determining an indication of multipath reflectionalong a path of signal propagation between the GNSS satellite and themobile device.
 2. The method of claim 1, further comprising: determininga utilization plan for signals associated with the GNSS satellite, basedon the indication of multipath reflection between the GNSS satellite andthe mobile device.
 3. The method of claim 2, wherein the utilizationplan comprises assigning a weight to signals or a position fix derivedfrom signals from the GNSS satellite in estimating a position for themobile device.
 4. The method of claim 2, wherein the utilization plancomprises utilizing signals from the GNSS satellite for estimating aposition for the mobile device.
 5. The method of claim 2, wherein theutilization plan comprises utilizing signals based on communicationprotocols other than the GNSS satellite for estimating a position forthe mobile device.
 6. The method of claim 2, wherein the utilizationplan is further applied to signals from one or more other GNSSsatellites from one or more GNSS constellations.
 7. The method of claim1, further comprising: receiving a right-handed circularly polarized(RHCP) signal and a left-handed circularly polarized (LHCP) signal, astime-multiplexed signals, over a single signal path from an antennasubsystem; generating the first indication of signal strength associatedwith the first polarization type from the RHCP signal; and generatingthe second indication of signal strength associated with the secondpolarization type from the LHCP signal.
 8. The method of claim 1,further comprising: receiving a right-handed circularly polarized (RHCP)signal over a first signal path from an antenna subsystem; receiving aleft-handed circularly polarized (LHCP) signal over a second signal pathfrom the antenna subsystem; generating the first indication of signalstrength associated with the first polarization type from the RHCPsignal; and generating the second indication of signal strengthassociated with the second polarization type from the LHCP signal. 9.The method of claim 1, further comprising: receiving a first linearlypolarized signal over a first signal path from an antenna subsystem;receiving second linearly polarized signal over a second signal pathfrom the antenna subsystem; converting the first linearly polarizedsignal and the second linearly polarized signal to a right-handedcircularly polarized (RHCP) signal and a left-handed circularlypolarized (LHCP) signal; generating the first indication of signalstrength associated with the first polarization type from the RHCPsignal; and generating the second indication of signal strengthassociated with the second polarization type from the LHCP signal. 10.The method of claim 1, further comprising: receiving a right-handedcircularly polarized (RHCP) signal and a left-handed circularlypolarized (LHCP) signal, as frequency-multiplexed signals, over a singlesignal path from an antenna subsystem; generating the first indicationof signal strength associated with the first polarization type from theRHCP signal; and generating the second indication of signal strengthassociated with the second polarization type from the LHCP signal. 11.The method of claim 1, further comprising: controlling one or moreswitches to select, at a first time, the one or more signals receivedfrom the GNSS satellite and select, at a second time, one or morewide-area-network (WAN) signals received at the mobile device using theone or more antennas.
 12. The method of claim 1, further comprising:receiving a right-handed circularly polarized (RHCP) signal and aleft-handed circularly polarized (LHCP) signal as digital data;generating the first indication of signal strength associated with thefirst polarization type from the RHCP signal; and generating the secondindication of signal strength associated with the second polarizationtype from the LHCP signal.
 13. The method of claim 1, wherein thedetermining of the indication of multipath reflection is further basedon a relative comparison between the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type.
 14. Themethod of claim 13, wherein the determining of the indication ofmultipath reflection is further based on prior measurement data relatingto the first indication of signal strength associated with the firstpolarization type and the second indication of signal strengthassociated with the second polarization type, the prior measurement datahaving been obtained by other mobile devices and being accessible to themobile device.
 15. The method of claim 1, further comprising determininga polarization profile based on the first indication of signal strengthassociated with the first polarization type and the second indication ofsignal strength associated with the second polarization type, thepolarization profile comprising a relationship among the firstindication of signal strength, the second indication of signal strength,a multipath characteristic associated with the one or more signalsreceived from the GNSS satellite, and an environmental context.
 16. Themethod of claim 15, further comprising determining, based at least onthe polarization profile and the indication of multipath reflection, apresence of a signal spoofing source associated with the one or moresignals received from the GNSS satellite.
 17. The method of claim 1,further comprising: determining, based on the first indication of signalstrength associated with the first polarization type and the secondindication of signal strength associated with the second polarizationtype, an amplification of the one or more signals received from the GNSSsatellite; and responsive to the determining of the amplification of theone or more signals, mitigating the amplification by adjusting receiptof at least one of the first polarization type or the secondpolarization type.
 18. A user equipment comprising: a basebandsubsystem; an antenna subsystem configured for signal communication withthe baseband subsystem, the antenna subsystem comprising a firstantenna, a second antenna, and a radio frequency (RF) coupler configuredto receive signal inputs from the first antenna and the second antennato output a signal having a first polarization type and a signal havinga second polarization type; and a processor, communicatively connectedto the baseband subsystem, the processor configured to: determine afirst indication of signal strength associated with the firstpolarization type and derived from one or more signals received from aGNSS satellite using the antenna subsystem; determine a secondindication of signal strength associated with the second polarizationtype and derived from the one or more signals received from the GNSSsatellite using the antenna subsystem; and based on the first indicationof signal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determine an indication of multipath reflection alonga path of signal propagation between the GNSS satellite and the userequipment.
 19. The user equipment of claim 18, wherein the basebandsubsystem comprises a first receiver and a second receiver, the firstreceiver configured to determine the first indication of signal strengthassociated with the first polarization type, the second receiverconfigured to determine the second indication of signal strengthassociated with the second polarization type.
 20. The user equipment ofclaim 18, wherein: the first antenna is configured to detect a signalcomponent having a vertical polarization; the second antenna isconfigured to detect a signal component having a horizontalpolarization; and the RF coupler is further configured to combine thesignal component having the vertical polarization and the signalcomponent having the horizontal polarization to output a circularlypolarized signal, the circularly polarized signal comprising aright-handed circularly polarized (RHCP) signal component and aleft-handed circularly polarized (LHCP) signal component.
 21. The userequipment of claim 18, wherein the processor is further configured to:receive a right-handed circularly polarized (RHCP) signal and aleft-handed circularly polarized (LHCP) signal, as time-multiplexedsignals, over a single signal path from the antenna subsystem; generatethe first indication of signal strength associated with the firstpolarization type from the RHCP signal; and generate the secondindication of signal strength associated with the second polarizationtype from the LHCP signal.
 22. The user equipment of claim 18, whereinthe processor is further configured to: receive a right-handedcircularly polarized (RHCP) signal and a left-handed circularlypolarized (LHCP) signal, as frequency-multiplexed signals, over a singlesignal path from the antenna subsystem; generate the first indication ofsignal strength associated with the first polarization type from theRHCP signal; and generate the second indication of signal strengthassociated with the second polarization type from the LHCP signal. 23.The user equipment of claim 18, wherein the determination of theindication of multipath reflection is further based on a relativecomparison between the first indication of signal strength associatedwith the first polarization type and the second indication of signalstrength associated with the second polarization type.
 24. Anon-transitory computer-readable apparatus comprising a storage medium,the storage medium comprising a plurality of instructions to, whenexecuted by a processor, cause a mobile device to: determine a firstindication of signal strength associated with a first polarization typeand derived from one or more signals received from a GNSS satelliteusing one or more antennas at the mobile device; determine a secondindication of signal strength associated with a second polarization typeand derived from the one or more signals received from the GNSSsatellite using the one or more antennas at the mobile device; and basedon the first indication of signal strength associated with the firstpolarization type and the second indication of signal strengthassociated with the second polarization type, determine an indication ofmultipath reflection along a path of signal propagation between the GNSSsatellite and the mobile device.
 25. The non-transitorycomputer-readable apparatus of claim 24, further comprising instructionsto, when executed by the processor, cause the mobile device to: receivea right-handed circularly polarized (RHCP) signal and a left-handedcircularly polarized (LHCP) signal, as time-multiplexed signals, over asingle signal path from an antenna subsystem; generate the firstindication of signal strength associated with the first polarizationtype from the RHCP signal; and generate the second indication of signalstrength associated with the second polarization type from the LHCPsignal.
 26. The non-transitory computer-readable apparatus of claim 24,further comprising instructions to, when executed by the processor,cause the mobile device to: receive a right-handed circularly polarized(RHCP) signal and a left-handed circularly polarized (LHCP) signal, asfrequency-multiplexed signals, over a single signal path from an antennasubsystem; generate the first indication of signal strength associatedwith the first polarization type from the RHCP signal; and generate thesecond indication of signal strength associated with the secondpolarization type from the LHCP signal.
 27. The non-transitorycomputer-readable apparatus of claim 24, wherein the determination ofthe indication of multipath reflection is further based on a relativecomparison between the first indication of signal strength associatedwith the first polarization type and the second indication of signalstrength associated with the second polarization type.
 28. Acomputerized apparatus comprising: means for determining a firstindication of signal strength associated with a first polarization typeand derived from one or more signals received from a GNSS satelliteusing one or more antennas; means for determining a second indication ofsignal strength associated with a second polarization type and derivedfrom the one or more signals received from the GNSS satellite using theone or more antennas; and means for, based on the first indication ofsignal strength associated with the first polarization type and thesecond indication of signal strength associated with the secondpolarization type, determining an indication of multipath reflectionalong a path of signal propagation from the GNSS satellite.
 29. Thecomputerized apparatus of claim 28, wherein the means for determiningthe first indication of signal strength associated with the firstpolarization type comprise a dedicated right-handed circularly polarized(RHCP) antenna, and the means for determining the second indication ofsignal strength associated with the second polarization type comprise adedicated left-handed circularly polarized (LHCP) antenna.
 30. Thecomputerized apparatus of claim 28, further comprising: means forreceiving the one or more signals from the GNSS satellite, the means forreceiving the one or more signals from the GNSS satellite comprising afirst antenna configured to detect a signal component having a verticalpolarization, and a second antenna configured to detect a signalcomponent having a horizontal polarization; and means for combining thesignal component having the vertical polarization and the signalcomponent having the horizontal polarization to output a circularlypolarized signal, the circularly polarized signal comprising aright-handed circularly polarized (RHCP) signal component and aleft-handed circularly polarized (LHCP) signal component.